Merge branch 'develop' into dependabot/github_actions/develop/actions/checkout-5.0.0

ci: [DEPENDABOT] bump actions/checkout from 4.3.0 to 5.0.0
Bumps [actions/checkout](https://github.com/actions/checkout) from 4.3.0 to 5.0.0. - [Release notes](https://github.com/actions/checkout/releases) - [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md) - [Commits](08eba0b27e...08c6903cd8) --- updated-dependencies: - dependency-name: actions/checkout dependency-version: 5.0.0 dependency-type: direct:production update-type: version-update:semver-major ... Signed-off-by: dependabot[bot] <support@github.com>
2025-11-19 11:15:50 +00:00 · 2025-10-28 16:02:14 +00:00 · 2025-10-27 10:21:04 +00:00
270 changed files with 8553 additions and 7703 deletions
--- a/.clang-format
+++ b/.clang-format
@@ -49,7 +49,6 @@ IndentFunctionDeclarationAfterType: false
 IndentWidth: 4
 IndentWrappedFunctionNames: false
 IndentRequiresClause: true
-InsertNewlineAtEOF: true
 RequiresClausePosition: OwnLine
 KeepEmptyLinesAtTheStartOfBlocks: false
 MaxEmptyLinesToKeep: 1
--- a/.cmake-format.yaml
+++ b/.cmake-format.yaml
@@ -54,7 +54,7 @@ format:
  _help_max_pargs_hwrap:
    - If a positional argument group contains more than this many
    - arguments, then force it to a vertical layout.
-  max_pargs_hwrap: 5
+  max_pargs_hwrap: 6
  _help_max_rows_cmdline:
    - If a cmdline positional group consumes more than this many
    - lines without nesting, then invalidate the layout (and nest)
--- a/.github/actions/build-docker-image/action.yml
+++ b/.github/actions/build-docker-image/action.yml
@@ -47,12 +47,12 @@ runs:
        username: ${{ github.repository_owner }}
        password: ${{ env.GITHUB_TOKEN }}

-    - uses: docker/setup-qemu-action@c7c53464625b32c7a7e944ae62b3e17d2b600130 # v3.7.0
+    - uses: docker/setup-qemu-action@29109295f81e9208d7d86ff1c6c12d2833863392 # v3.6.0
      with:
        cache-image: false
    - uses: docker/setup-buildx-action@e468171a9de216ec08956ac3ada2f0791b6bd435 # v3.11.1

-    - uses: docker/metadata-action@318604b99e75e41977312d83839a89be02ca4893 # v5.9.0
+    - uses: docker/metadata-action@c1e51972afc2121e065aed6d45c65596fe445f3f # v5.8.0
      id: meta
      with:
        images: ${{ inputs.images }}
--- a/.github/actions/cache-key/action.yml
+++ b/.github/actions/cache-key/action.yml
@@ -1,41 +0,0 @@
-name: Cache key
-description: Generate cache key for ccache
-
-inputs:
-  conan_profile:
-    description: Conan profile name
-    required: true
-  build_type:
-    description: Current build type (e.g. Release, Debug)
-    required: true
-    default: Release
-  code_coverage:
-    description: Whether code coverage is on
-    required: true
-    default: "false"
-
-outputs:
-  key:
-    description: Generated cache key for ccache
-    value: ${{ steps.key_without_commit.outputs.key }}-${{ steps.git_common_ancestor.outputs.commit }}
-  restore_keys:
-    description: Cache restore keys for fallback
-    value: ${{ steps.key_without_commit.outputs.key }}
-
-runs:
-  using: composite
-  steps:
-    - name: Find common commit
-      id: git_common_ancestor
-      uses: ./.github/actions/git-common-ancestor
-
-    - name: Set cache key without commit
-      id: key_without_commit
-      shell: bash
-      env:
-        RUNNER_OS: ${{ runner.os }}
-        BUILD_TYPE: ${{ inputs.build_type }}
-        CODE_COVERAGE: ${{ inputs.code_coverage == 'true' && '-code_coverage' || '' }}
-        CONAN_PROFILE: ${{ inputs.conan_profile }}
-      run: |
-        echo "key=clio-ccache-${RUNNER_OS}-${BUILD_TYPE}${CODE_COVERAGE}-${CONAN_PROFILE}-develop" >> "${GITHUB_OUTPUT}"
--- a/.github/actions/cmake/action.yml
+++ b/.github/actions/cmake/action.yml
@@ -44,7 +44,6 @@ runs:
    - name: Run cmake
      shell: bash
      env:
-        BUILD_DIR: "${{ inputs.build_dir }}"
        BUILD_TYPE: "${{ inputs.build_type }}"
        SANITIZER_OPTION: |-
          ${{ endsWith(inputs.conan_profile, '.asan') && '-Dsan=address' ||
@@ -59,7 +58,7 @@ runs:
        PACKAGE: "${{ inputs.package == 'true' && 'ON' || 'OFF' }}"
      run: |
        cmake \
-          -B "${BUILD_DIR}" \
+          -B ${{inputs.build_dir}} \
          -S . \
          -G Ninja \
          -DCMAKE_TOOLCHAIN_FILE:FILEPATH=build/generators/conan_toolchain.cmake \
--- a/.github/actions/conan/action.yml
+++ b/.github/actions/conan/action.yml
@@ -28,14 +28,11 @@ runs:
    - name: Run conan
      shell: bash
      env:
-        BUILD_DIR: "${{ inputs.build_dir }}"
        CONAN_BUILD_OPTION: "${{ inputs.force_conan_source_build == 'true' && '*' || 'missing' }}"
-        BUILD_TYPE: "${{ inputs.build_type }}"
-        CONAN_PROFILE: "${{ inputs.conan_profile }}"
      run: |
        conan \
          install . \
-          -of "${BUILD_DIR}" \
-          -b "${CONAN_BUILD_OPTION}" \
-          -s "build_type=${BUILD_TYPE}" \
-          --profile:all "${CONAN_PROFILE}"
+          -of build \
+          -b "$CONAN_BUILD_OPTION" \
+          -s "build_type=${{ inputs.build_type }}" \
+          --profile:all "${{ inputs.conan_profile }}"
--- a/.github/actions/restore-cache/action.yml
+++ b/.github/actions/restore-cache/action.yml
@@ -0,0 +1,38 @@
+name: Restore cache
+description: Find and restores ccache cache
+
+inputs:
+  conan_profile:
+    description: Conan profile name
+    required: true
+  ccache_dir:
+    description: Path to .ccache directory
+    required: true
+  build_type:
+    description: Current build type (e.g. Release, Debug)
+    required: true
+    default: Release
+  code_coverage:
+    description: Whether code coverage is on
+    required: true
+    default: "false"
+
+outputs:
+  ccache_cache_hit:
+    description: True if ccache cache has been downloaded
+    value: ${{ steps.ccache_cache.outputs.cache-hit }}
+
+runs:
+  using: composite
+  steps:
+    - name: Find common commit
+      id: git_common_ancestor
+      uses: ./.github/actions/git-common-ancestor
+
+    - name: Restore ccache cache
+      uses: actions/cache/restore@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+      id: ccache_cache
+      if: ${{ env.CCACHE_DISABLE != '1' }}
+      with:
+        path: ${{ inputs.ccache_dir }}
+        key: clio-ccache-${{ runner.os }}-${{ inputs.build_type }}${{ inputs.code_coverage == 'true' && '-code_coverage' || '' }}-${{ inputs.conan_profile }}-develop-${{ steps.git_common_ancestor.outputs.commit }}
--- a/.github/actions/save-cache/action.yml
+++ b/.github/actions/save-cache/action.yml
@@ -0,0 +1,38 @@
+name: Save cache
+description: Save ccache cache for develop branch
+
+inputs:
+  conan_profile:
+    description: Conan profile name
+    required: true
+  ccache_dir:
+    description: Path to .ccache directory
+    required: true
+  build_type:
+    description: Current build type (e.g. Release, Debug)
+    required: true
+    default: Release
+  code_coverage:
+    description: Whether code coverage is on
+    required: true
+    default: "false"
+
+  ccache_cache_hit:
+    description: Whether ccache cache has been downloaded
+    required: true
+  ccache_cache_miss_rate:
+    description: How many ccache cache misses happened
+
+runs:
+  using: composite
+  steps:
+    - name: Find common commit
+      id: git_common_ancestor
+      uses: ./.github/actions/git-common-ancestor
+
+    - name: Save ccache cache
+      if: ${{ inputs.ccache_cache_hit != 'true' || inputs.ccache_cache_miss_rate == '100.0' }}
+      uses: actions/cache/save@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+      with:
+        path: ${{ inputs.ccache_dir }}
+        key: clio-ccache-${{ runner.os }}-${{ inputs.build_type }}${{ inputs.code_coverage == 'true' && '-code_coverage' || '' }}-${{ inputs.conan_profile }}-develop-${{ steps.git_common_ancestor.outputs.commit }}
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -105,7 +105,20 @@ updates:
    target-branch: develop

  - package-ecosystem: github-actions
-    directory: .github/actions/cache-key/
+    directory: .github/actions/restore-cache/
+    schedule:
+      interval: weekly
+      day: monday
+      time: "04:00"
+      timezone: Etc/GMT
+    reviewers:
+      - XRPLF/clio-dev-team
+    commit-message:
+      prefix: "ci: [DEPENDABOT] "
+    target-branch: develop
+
+  - package-ecosystem: github-actions
+    directory: .github/actions/save-cache/
    schedule:
      interval: weekly
      day: monday
--- a/.github/scripts/conan/apple-clang-17.profile
+++ b/.github/scripts/conan/apple-clang-17.profile
@@ -4,7 +4,7 @@ build_type=Release
 compiler=apple-clang
 compiler.cppstd=20
 compiler.libcxx=libc++
-compiler.version=17.0
+compiler.version=17
 os=Macos

 [conf]
--- a/.github/scripts/conan/generate_matrix.py
+++ b/.github/scripts/conan/generate_matrix.py
@@ -4,7 +4,7 @@ import json

 LINUX_OS = ["heavy", "heavy-arm64"]
 LINUX_CONTAINERS = [
-    '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+    '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
 ]
 LINUX_COMPILERS = ["gcc", "clang"]

--- a/.github/workflows/build-clio-docker-image.yml
+++ b/.github/workflows/build-clio-docker-image.yml
@@ -38,10 +38,6 @@ on:
        description: Whether to strip clio binary
        default: true

-defaults:
-  run:
-    shell: bash
-
 jobs:
  build_and_publish_image:
    name: Build and publish image
@@ -59,6 +55,7 @@ jobs:

      - name: Download Clio binary from url
        if: ${{ inputs.clio_server_binary_url != null }}
+        shell: bash
        env:
          BINARY_URL: ${{ inputs.clio_server_binary_url }}
          BINARY_SHA256: ${{ inputs.binary_sha256 }}
@@ -69,6 +66,7 @@ jobs:
            exit 1
          fi
      - name: Unpack binary
+        shell: bash
        run: |
          sudo apt update && sudo apt install -y tar unzip
          cd docker/clio/artifact
@@ -85,6 +83,7 @@ jobs:

      - name: Strip binary
        if: ${{ inputs.strip_binary }}
+        shell: bash
        run: strip ./docker/clio/clio_server

      - name: Set GHCR_REPO
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -33,10 +33,6 @@ concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.ref == 'refs/heads/develop' && github.run_number || 'branch' }}
  cancel-in-progress: true

-defaults:
-  run:
-    shell: bash
-
 jobs:
  build-and-test:
    name: Build and Test
@@ -49,7 +45,7 @@ jobs:
        build_type: [Release, Debug]
        container:
          [
-            '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }',
+            '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }',
          ]
        static: [true]

@@ -79,11 +75,11 @@ jobs:
    uses: ./.github/workflows/reusable-build.yml
    with:
      runs_on: heavy
-      container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+      container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
      conan_profile: gcc
      build_type: Debug
      download_ccache: true
-      upload_ccache: true
+      upload_ccache: false
      code_coverage: true
      static: true
      upload_clio_server: false
@@ -98,7 +94,7 @@ jobs:
    uses: ./.github/workflows/reusable-build.yml
    with:
      runs_on: heavy
-      container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+      container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
      conan_profile: gcc
      build_type: Release
      download_ccache: true
@@ -115,7 +111,7 @@ jobs:
    needs: build-and-test
    runs-on: heavy
    container:
-      image: ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+      image: ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d

    steps:
      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
@@ -125,6 +121,7 @@ jobs:
          name: clio_server_Linux_Release_gcc

      - name: Compare Config Description
+        shell: bash
        run: |
          repoConfigFile=docs/config-description.md
          configDescriptionFile=config_description_new.md
--- a/.github/workflows/check-libxrpl.yml
+++ b/.github/workflows/check-libxrpl.yml
@@ -12,16 +12,12 @@ concurrency:
 env:
  CONAN_PROFILE: gcc

-defaults:
-  run:
-    shell: bash
-
 jobs:
  build:
    name: Build Clio / `libXRPL ${{ github.event.client_payload.version }}`
    runs-on: heavy
    container:
-      image: ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+      image: ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d

    steps:
      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
@@ -29,16 +25,18 @@ jobs:
          fetch-depth: 0

      - name: Prepare runner
-        uses: XRPLF/actions/.github/actions/prepare-runner@8abb0722cbff83a9a2dc7d06c473f7a4964b7382
+        uses: XRPLF/actions/.github/actions/prepare-runner@7951b682e5a2973b28b0719a72f01fc4b0d0c34f
        with:
          disable_ccache: true

      - name: Update libXRPL version requirement
+        shell: bash
        run: |
          sed -i.bak -E "s|'xrpl/[a-zA-Z0-9\\.\\-]+'|'xrpl/${{ github.event.client_payload.conan_ref }}'|g" conanfile.py
          rm -f conanfile.py.bak

      - name: Update conan lockfile
+        shell: bash
        run: |
          conan lock create . --profile:all ${{ env.CONAN_PROFILE }}

@@ -69,7 +67,7 @@ jobs:
    needs: build
    runs-on: heavy
    container:
-      image: ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+      image: ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d

    steps:
      - uses: actions/download-artifact@018cc2cf5baa6db3ef3c5f8a56943fffe632ef53 # v6.0.0
--- a/.github/workflows/check-pr-title.yml
+++ b/.github/workflows/check-pr-title.yml
@@ -5,10 +5,6 @@ on:
    types: [opened, edited, reopened, synchronize]
    branches: [develop]

-defaults:
-  run:
-    shell: bash
-
 jobs:
  check_title:
    runs-on: ubuntu-latest
--- a/.github/workflows/clang-tidy.yml
+++ b/.github/workflows/clang-tidy.yml
@@ -22,16 +22,12 @@ env:
  CONAN_PROFILE: clang
  LLVM_TOOLS_VERSION: 20

-defaults:
-  run:
-    shell: bash
-
 jobs:
  clang_tidy:
    if: github.event_name != 'push' || contains(github.event.head_commit.message, 'clang-tidy auto fixes')
    runs-on: heavy
    container:
-      image: ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+      image: ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d

    permissions:
      contents: write
@@ -44,10 +40,17 @@ jobs:
          fetch-depth: 0

      - name: Prepare runner
-        uses: XRPLF/actions/.github/actions/prepare-runner@8abb0722cbff83a9a2dc7d06c473f7a4964b7382
+        uses: XRPLF/actions/.github/actions/prepare-runner@7951b682e5a2973b28b0719a72f01fc4b0d0c34f
        with:
          disable_ccache: true

+      - name: Restore cache
+        uses: ./.github/actions/restore-cache
+        id: restore_cache
+        with:
+          conan_profile: ${{ env.CONAN_PROFILE }}
+          ccache_dir: ${{ env.CCACHE_DIR }}
+
      - name: Run conan
        uses: ./.github/actions/conan
        with:
@@ -64,18 +67,21 @@ jobs:

      - name: Run clang-tidy
        continue-on-error: true
+        shell: bash
        id: run_clang_tidy
        run: |
          run-clang-tidy-${{ env.LLVM_TOOLS_VERSION }} -p build -j "${{ steps.nproc.outputs.nproc }}" -fix -quiet 1>output.txt

      - name: Fix local includes and clang-format style
        if: ${{ steps.run_clang_tidy.outcome != 'success' }}
+        shell: bash
        run: |
          pre-commit run --all-files fix-local-includes || true
          pre-commit run --all-files clang-format || true

      - name: Print issues found
        if: ${{ steps.run_clang_tidy.outcome != 'success' }}
+        shell: bash
        run: |
          sed -i '/error\||/!d' ./output.txt
          cat output.txt
@@ -120,4 +126,5 @@ jobs:

      - name: Fail the job
        if: ${{ steps.run_clang_tidy.outcome != 'success' }}
+        shell: bash
        run: exit 1
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -10,15 +10,11 @@ concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

-defaults:
-  run:
-    shell: bash
-
 jobs:
  build:
    runs-on: ubuntu-latest
    container:
-      image: ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+      image: ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d

    steps:
      - name: Checkout
@@ -27,7 +23,7 @@ jobs:
          lfs: true

      - name: Prepare runner
-        uses: XRPLF/actions/.github/actions/prepare-runner@8abb0722cbff83a9a2dc7d06c473f7a4964b7382
+        uses: XRPLF/actions/.github/actions/prepare-runner@7951b682e5a2973b28b0719a72f01fc4b0d0c34f
        with:
          disable_ccache: true

--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -23,10 +23,6 @@ concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

-defaults:
-  run:
-    shell: bash
-
 jobs:
  build-and-test:
    name: Build and Test
@@ -43,17 +39,17 @@ jobs:
            conan_profile: gcc
            build_type: Release
            static: true
-            container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+            container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
          - os: heavy
            conan_profile: gcc
            build_type: Debug
            static: true
-            container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+            container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
          - os: heavy
            conan_profile: gcc.ubsan
            build_type: Release
            static: false
-            container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+            container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'

    uses: ./.github/workflows/reusable-build-test.yml
    with:
@@ -77,7 +73,7 @@ jobs:
        include:
          - os: heavy
            conan_profile: clang
-            container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+            container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
            static: true
          - os: macos15
            conan_profile: apple-clang
@@ -97,29 +93,18 @@ jobs:
      targets: all
      analyze_build_time: true

-  get_date:
-    name: Get Date
-    runs-on: ubuntu-latest
-    outputs:
-      date: ${{ steps.get_date.outputs.date }}
-    steps:
-      - name: Get current date
-        id: get_date
-        run: |
-          echo "date=$(date +'%Y%m%d')" >> $GITHUB_OUTPUT
-
  nightly_release:
-    needs: [build-and-test, get_date]
+    needs: build-and-test
    uses: ./.github/workflows/reusable-release.yml
    with:
-      delete_pattern: "nightly-*"
+      overwrite_release: true
      prerelease: true
-      title: "Clio development build (nightly-${{ needs.get_date.outputs.date }})"
-      version: nightly-${{ needs.get_date.outputs.date }}
+      title: "Clio development (nightly) build"
+      version: nightly
      header: >
        > **Note:** Please remember that this is a development release and it is not recommended for production use.

-        Changelog (including previous releases): <https://github.com/XRPLF/clio/commits/nightly-${{ needs.get_date.outputs.date }}>
+        Changelog (including previous releases): <https://github.com/XRPLF/clio/commits/nightly>
      generate_changelog: false
      draft: false

--- a/.github/workflows/pre-commit-autoupdate.yml
+++ b/.github/workflows/pre-commit-autoupdate.yml
@@ -1,8 +1,8 @@
 name: Pre-commit auto-update

 on:
+  # every first day of the month
  schedule:
-    # every first day of the month
    - cron: "0 0 1 * *"
  pull_request:
    branches: [release/*, develop]
--- a/.github/workflows/pre-commit.yml
+++ b/.github/workflows/pre-commit.yml
@@ -11,4 +11,4 @@ jobs:
    uses: XRPLF/actions/.github/workflows/pre-commit.yml@34790936fae4c6c751f62ec8c06696f9c1a5753a
    with:
      runs_on: heavy
-      container: '{ "image": "ghcr.io/xrplf/clio-pre-commit:c117f470f2ef954520ab5d1c8a5ed2b9e68d6f8a" }'
+      container: '{ "image": "ghcr.io/xrplf/clio-pre-commit:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -29,7 +29,7 @@ jobs:
            conan_profile: gcc
            build_type: Release
            static: true
-            container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+            container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'

    uses: ./.github/workflows/reusable-build-test.yml
    with:
@@ -49,7 +49,7 @@ jobs:
    needs: build-and-test
    uses: ./.github/workflows/reusable-release.yml
    with:
-      delete_pattern: ""
+      overwrite_release: false
      prerelease: ${{ contains(github.ref_name, '-') }}
      title: "${{ github.ref_name }}"
      version: "${{ github.ref_name }}"
--- a/.github/workflows/reusable-build.yml
+++ b/.github/workflows/reusable-build.yml
@@ -75,10 +75,6 @@ on:
      CODECOV_TOKEN:
        required: false

-defaults:
-  run:
-    shell: bash
-
 jobs:
  build:
    name: Build
@@ -99,31 +95,24 @@ jobs:
          ref: ${{ github.ref }}

      - name: Prepare runner
-        uses: XRPLF/actions/.github/actions/prepare-runner@8abb0722cbff83a9a2dc7d06c473f7a4964b7382
+        uses: XRPLF/actions/.github/actions/prepare-runner@7951b682e5a2973b28b0719a72f01fc4b0d0c34f
        with:
          disable_ccache: ${{ !inputs.download_ccache }}

      - name: Setup conan on macOS
        if: ${{ runner.os == 'macOS' }}
+        shell: bash
        run: ./.github/scripts/conan/init.sh

-      - name: Generate cache key
-        uses: ./.github/actions/cache-key
-        id: cache_key
-        with:
-          conan_profile: ${{ inputs.conan_profile }}
-          build_type: ${{ inputs.build_type }}
-          code_coverage: ${{ inputs.code_coverage }}
-
-      - name: Restore ccache cache
+      - name: Restore cache
        if: ${{ inputs.download_ccache }}
-        uses: actions/cache/restore@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+        uses: ./.github/actions/restore-cache
        id: restore_cache
        with:
-          path: ${{ env.CCACHE_DIR }}
-          key: ${{ steps.cache_key.outputs.key }}
-          restore-keys: |
-            ${{ steps.cache_key.outputs.restore_keys }}
+          conan_profile: ${{ inputs.conan_profile }}
+          ccache_dir: ${{ env.CCACHE_DIR }}
+          build_type: ${{ inputs.build_type }}
+          code_coverage: ${{ inputs.code_coverage }}

      - name: Run conan
        uses: ./.github/actions/conan
@@ -152,6 +141,7 @@ jobs:
          ClangBuildAnalyzer --all build/ build_time_report.bin
          ClangBuildAnalyzer --analyze build_time_report.bin > build_time_report.txt
          cat build_time_report.txt
+        shell: bash

      - name: Upload build time analyze report
        if: ${{ inputs.analyze_build_time }}
@@ -162,6 +152,7 @@ jobs:

      - name: Show ccache's statistics
        if: ${{ inputs.download_ccache }}
+        shell: bash
        id: ccache_stats
        run: |
          ccache -s > /tmp/ccache.stats
@@ -169,13 +160,6 @@ jobs:
          echo "miss_rate=${miss_rate}" >> $GITHUB_OUTPUT
          cat /tmp/ccache.stats

-      - name: Save ccache cache
-        if: ${{ inputs.upload_ccache && github.ref == 'refs/heads/develop' && (steps.restore_cache.outputs.cache-hit != 'true' || steps.ccache_stats.outputs.miss_rate == '100.0') }}
-        uses: actions/cache/save@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
-        with:
-          path: ${{ env.CCACHE_DIR }}
-          key: ${{ steps.cache_key.outputs.key }}
-
      - name: Strip unit_tests
        if: ${{ !endsWith(inputs.conan_profile, 'san') && !inputs.code_coverage && !inputs.analyze_build_time }}
        run: strip build/clio_tests
@@ -212,6 +196,18 @@ jobs:
          name: clio_deb_package_${{ runner.os }}_${{ inputs.build_type }}_${{ inputs.conan_profile }}
          path: build/*.deb

+      - name: Save cache
+        if: ${{ inputs.upload_ccache && github.ref == 'refs/heads/develop' }}
+        uses: ./.github/actions/save-cache
+        with:
+          conan_profile: ${{ inputs.conan_profile }}
+          ccache_dir: ${{ env.CCACHE_DIR }}
+          build_type: ${{ inputs.build_type }}
+          code_coverage: ${{ inputs.code_coverage }}
+
+          ccache_cache_hit: ${{ steps.restore_cache.outputs.ccache_cache_hit }}
+          ccache_cache_miss_rate: ${{ steps.ccache_stats.outputs.miss_rate }}
+
      # This is run as part of the build job, because it requires the following:
      # - source code
      # - conan packages
@@ -224,6 +220,7 @@ jobs:

      - name: Verify expected version
        if: ${{ inputs.expected_version != '' }}
+        shell: bash
        env:
          INPUT_EXPECTED_VERSION: ${{ inputs.expected_version }}
        run: |
--- a/.github/workflows/reusable-release.yml
+++ b/.github/workflows/reusable-release.yml
@@ -3,10 +3,10 @@ name: Make release
 on:
  workflow_call:
    inputs:
-      delete_pattern:
-        description: "Pattern to delete previous releases"
+      overwrite_release:
+        description: "Overwrite the current release and tag"
        required: true
-        type: string
+        type: boolean

      prerelease:
        description: "Create a prerelease"
@@ -38,15 +38,11 @@ on:
        required: true
        type: boolean

-defaults:
-  run:
-    shell: bash
-
 jobs:
  release:
    runs-on: heavy
    container:
-      image: ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+      image: ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d
    env:
      GH_REPO: ${{ github.repository }}
      GH_TOKEN: ${{ github.token }}
@@ -60,7 +56,7 @@ jobs:
          fetch-depth: 0

      - name: Prepare runner
-        uses: XRPLF/actions/.github/actions/prepare-runner@8abb0722cbff83a9a2dc7d06c473f7a4964b7382
+        uses: XRPLF/actions/.github/actions/prepare-runner@7951b682e5a2973b28b0719a72f01fc4b0d0c34f
        with:
          disable_ccache: true

@@ -70,6 +66,7 @@ jobs:
          pattern: clio_server_*

      - name: Create release notes
+        shell: bash
        env:
          RELEASE_HEADER: ${{ inputs.header }}
        run: |
@@ -78,6 +75,7 @@ jobs:
          printf '%s\n' "${RELEASE_HEADER}" >> "${RUNNER_TEMP}/release_notes.md"

      - name: Generate changelog
+        shell: bash
        if: ${{ inputs.generate_changelog }}
        run: |
          LAST_TAG="$(gh release view --json tagName -q .tagName --repo XRPLF/clio)"
@@ -87,6 +85,7 @@ jobs:
          cat CHANGELOG.md >> "${RUNNER_TEMP}/release_notes.md"

      - name: Prepare release artifacts
+        shell: bash
        run: .github/scripts/prepare-release-artifacts.sh release_artifacts

      - name: Upload release notes
@@ -95,21 +94,18 @@ jobs:
          name: release_notes_${{ inputs.version }}
          path: "${RUNNER_TEMP}/release_notes.md"

-      - name: Remove previous release with a pattern
-        if: ${{ github.event_name != 'pull_request' && inputs.delete_pattern != '' }}
+      - name: Remove current release and tag
+        if: ${{ github.event_name != 'pull_request' && inputs.overwrite_release }}
+        shell: bash
        env:
-          DELETE_PATTERN: ${{ inputs.delete_pattern }}
+          RELEASE_VERSION: ${{ inputs.version }}
        run: |
-          RELEASES_TO_DELETE=$(gh release list --limit 50 --repo "${GH_REPO}" | grep -E "${DELETE_PATTERN}" | awk -F'\t' '{print $3}' || true)
-          if [ -n "$RELEASES_TO_DELETE" ]; then
-            for RELEASE in $RELEASES_TO_DELETE; do
-              echo "Deleting release: $RELEASE"
-              gh release delete "$RELEASE" --repo "${GH_REPO}" --yes --cleanup-tag
-            done
-          fi
+          gh release delete "${RELEASE_VERSION}" --yes || true
+          git push origin :"${RELEASE_VERSION}" || true

      - name: Publish release
        if: ${{ github.event_name != 'pull_request' }}
+        shell: bash
        env:
          RELEASE_VERSION: ${{ inputs.version }}
          PRERELEASE_OPTION: ${{ inputs.prerelease && '--prerelease' || '' }}
--- a/.github/workflows/reusable-test.yml
+++ b/.github/workflows/reusable-test.yml
@@ -33,10 +33,6 @@ on:
        required: true
        type: boolean

-defaults:
-  run:
-    shell: bash
-
 jobs:
  unit_tests:
    name: Unit testing
@@ -47,7 +43,7 @@ jobs:

    env:
      # TODO: remove completely when we have fixed all currently existing issues with sanitizers
-      SANITIZER_IGNORE_ERRORS: ${{ endsWith(inputs.conan_profile, '.tsan') }}
+      SANITIZER_IGNORE_ERRORS: ${{ endsWith(inputs.conan_profile, '.tsan') || (inputs.conan_profile == 'gcc.asan' && inputs.build_type == 'Release') }}

    steps:
      - name: Cleanup workspace
@@ -63,6 +59,7 @@ jobs:
          name: clio_tests_${{ runner.os }}_${{ inputs.build_type }}_${{ inputs.conan_profile }}

      - name: Make clio_tests executable
+        shell: bash
        run: chmod +x ./clio_tests

      - name: Run clio_tests (regular)
@@ -75,6 +72,7 @@ jobs:

      - name: Check for sanitizer report
        if: ${{ env.SANITIZER_IGNORE_ERRORS == 'true' }}
+        shell: bash
        id: check_report
        run: |
          if ls .sanitizer-report/* 1> /dev/null 2>&1; then
--- a/.github/workflows/reusable-upload-coverage-report.yml
+++ b/.github/workflows/reusable-upload-coverage-report.yml
@@ -6,10 +6,6 @@ on:
      CODECOV_TOKEN:
        required: true

-defaults:
-  run:
-    shell: bash
-
 jobs:
  upload_report:
    name: Upload report
--- a/.github/workflows/sanitizers.yml
+++ b/.github/workflows/sanitizers.yml
@@ -44,7 +44,7 @@ jobs:
    uses: ./.github/workflows/reusable-build-test.yml
    with:
      runs_on: heavy
-      container: '{ "image": "ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8" }'
+      container: '{ "image": "ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d" }'
      download_ccache: false
      upload_ccache: false
      conan_profile: ${{ matrix.compiler }}${{ matrix.sanitizer_ext }}
--- a/.github/workflows/update-docker-ci.yml
+++ b/.github/workflows/update-docker-ci.yml
@@ -33,10 +33,6 @@ env:
  GCC_MAJOR_VERSION: 15
  GCC_VERSION: 15.2.0

-defaults:
-  run:
-    shell: bash
-
 jobs:
  repo:
    name: Calculate repo name
--- a/.github/workflows/upload-conan-deps.yml
+++ b/.github/workflows/upload-conan-deps.yml
@@ -40,10 +40,6 @@ concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

-defaults:
-  run:
-    shell: bash
-
 jobs:
  generate-matrix:
    runs-on: ubuntu-latest
@@ -76,12 +72,13 @@ jobs:
      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0

      - name: Prepare runner
-        uses: XRPLF/actions/.github/actions/prepare-runner@8abb0722cbff83a9a2dc7d06c473f7a4964b7382
+        uses: XRPLF/actions/.github/actions/prepare-runner@7951b682e5a2973b28b0719a72f01fc4b0d0c34f
        with:
          disable_ccache: true

      - name: Setup conan on macOS
        if: ${{ runner.os == 'macOS' }}
+        shell: bash
        run: ./.github/scripts/conan/init.sh

      - name: Show conan profile
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -11,10 +11,7 @@
 #
 # See https://pre-commit.com for more information
 # See https://pre-commit.com/hooks.html for more hooks
-exclude: |
-  (?x)^(
-    docs/doxygen-awesome-theme/.*
-  )$
+exclude: ^(docs/doxygen-awesome-theme/|conan\.lock$)

 repos:
  # `pre-commit sample-config` default hooks
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -75,11 +75,10 @@ if (san)
  endif ()
  target_compile_options(clio_options INTERFACE ${SAN_OPTIMIZATION_FLAG} ${SAN_FLAG} -fno-omit-frame-pointer)

-  if (san STREQUAL "address")
-    # ASAN needs these definitions as well as correct b2 flags in conan profile for sanitizers
-    target_compile_definitions(clio_options INTERFACE BOOST_USE_ASAN=1 BOOST_USE_UCONTEXT=1)
-  endif ()
-
+  target_compile_definitions(
+    clio_options INTERFACE $<$<STREQUAL:${san},address>:SANITIZER=ASAN> $<$<STREQUAL:${san},thread>:SANITIZER=TSAN>
+                           $<$<STREQUAL:${san},memory>:SANITIZER=MSAN> $<$<STREQUAL:${san},undefined>:SANITIZER=UBSAN>
+  )
  target_link_libraries(clio_options INTERFACE ${SAN_FLAG} ${SAN_LIB})
 endif ()

--- a/conan.lock
+++ b/conan.lock
@@ -3,7 +3,7 @@
    "requires": [
        "zlib/1.3.1#b8bc2603263cf7eccbd6e17e66b0ed76%1756234269.497",
        "xxhash/0.8.3#681d36a0a6111fc56e5e45ea182c19cc%1756234289.683",
-        "xrpl/3.0.0-rc1#f5c8ecd42bdf511ad36f57bc702dacd2%1762975621.294",
+        "xrpl/2.6.1#973af2bf9631f239941dd9f5a100bb84%1759275059.342",
        "sqlite3/3.49.1#8631739a4c9b93bd3d6b753bac548a63%1756234266.869",
        "spdlog/1.15.3#3ca0e9e6b83af4d0151e26541d140c86%1754401846.61",
        "soci/4.0.3#a9f8d773cd33e356b5879a4b0564f287%1756234262.318",
@@ -11,7 +11,7 @@
        "rapidjson/cci.20220822#1b9d8c2256876a154172dc5cfbe447c6%1754325007.656",
        "protobuf/3.21.12#d927114e28de9f4691a6bbcdd9a529d1%1756234251.614",
        "openssl/1.1.1w#a8f0792d7c5121b954578a7149d23e03%1756223730.729",
-        "nudb/2.0.9#fb8dfd1a5557f5e0528114c2da17721e%1763150366.909",
+        "nudb/2.0.9#c62cfd501e57055a7e0d8ee3d5e5427d%1756234237.107",
        "minizip/1.2.13#9e87d57804bd372d6d1e32b1871517a3%1754325004.374",
        "lz4/1.10.0#59fc63cac7f10fbe8e05c7e62c2f3504%1756234228.999",
        "libuv/1.46.0#dc28c1f653fa197f00db5b577a6f6011%1754325003.592",
@@ -45,7 +45,7 @@
        ],
        "protobuf/3.21.12": [
            null,
-            "protobuf/3.21.12#d927114e28de9f4691a6bbcdd9a529d1"
+            "protobuf/3.21.12"
        ],
        "lz4/1.9.4": [
            "lz4/1.10.0"
@@ -55,4 +55,4 @@
        ]
    },
    "config_requires": []
-}
+}
--- a/conanfile.py
+++ b/conanfile.py
@@ -18,7 +18,7 @@ class ClioConan(ConanFile):
        'protobuf/3.21.12',
        'grpc/1.50.1',
        'openssl/1.1.1w',
-        'xrpl/3.0.0-rc1',
+        'xrpl/2.6.1',
        'zlib/1.3.1',
        'libbacktrace/cci.20210118',
        'spdlog/1.15.3',
--- a/docker/ci/Dockerfile
+++ b/docker/ci/Dockerfile
@@ -55,11 +55,8 @@ RUN pip install -q --no-cache-dir \
        # lxml 6.0.0 is not compatible with our image
        'lxml<6.0.0' \
        cmake \
-        conan==2.22.1 \
-        gcovr \
-        # We're adding pre-commit to this image as well,
-        # because clang-tidy workflow requires it
-        pre-commit
+        conan==2.20.1 \
+        gcovr

 # Install LLVM tools
 ARG LLVM_TOOLS_VERSION=20
--- a/docker/ci/README.md
+++ b/docker/ci/README.md
@@ -5,17 +5,17 @@ It is used in [Clio Github Actions](https://github.com/XRPLF/clio/actions) but c

 The image is based on Ubuntu 20.04 and contains:

- ccache 4.12.1
+- ccache 4.11.3
 - Clang 19
 - ClangBuildAnalyzer 1.6.0
- Conan 2.22.1
- Doxygen 1.15.0
+- Conan 2.20.1
+- Doxygen 1.14
 - GCC 15.2.0
 - GDB 16.3
- gh 2.82.1
- git-cliff 2.10.1
- mold 2.40.4
- Python 3.8
+- gh 2.74
+- git-cliff 2.9.1
+- mold 2.40.1
+- Python 3.13
 - and some other useful tools

 Conan is set up to build Clio without any additional steps.
--- a/docker/ci/conan/sanitizer_template.profile
+++ b/docker/ci/conan/sanitizer_template.profile
@@ -3,9 +3,6 @@
 {% set sanitizer_opt_map = {"asan": "address", "tsan": "thread", "ubsan": "undefined"} %}
 {% set sanitizer = sanitizer_opt_map[sani] %}

-{% set sanitizer_b2_flags_map = {"address": "define=BOOST_USE_ASAN=1 context-impl=ucontext address-sanitizer=on", "thread": "thread-sanitizer=on", "undefined": "undefined-sanitizer=on"} %}
-{% set sanitizer_b2_flags_str = sanitizer_b2_flags_map[sanitizer] %}
-
 {% set sanitizer_build_flags_str = "-fsanitize=" ~ sanitizer ~ " -g -O1 -fno-omit-frame-pointer" %}
 {% set sanitizer_build_flags = sanitizer_build_flags_str.split(' ') %}
 {% set sanitizer_link_flags_str = "-fsanitize=" ~ sanitizer %}
@@ -14,8 +11,7 @@
 include({{ compiler }})

 [options]
-boost/*:extra_b2_flags="{{ sanitizer_b2_flags_str }}"
-boost/*:without_context=False
+boost/*:extra_b2_flags="cxxflags=\"{{ sanitizer_build_flags_str }}\" linkflags=\"{{ sanitizer_link_flags_str }}\""
 boost/*:without_stacktrace=True

 [conf]
--- a/docker/compilers/gcc/Dockerfile
+++ b/docker/compilers/gcc/Dockerfile
@@ -8,7 +8,7 @@ ARG UBUNTU_VERSION

 ARG GCC_MAJOR_VERSION

-ARG BUILD_VERSION=0
+ARG BUILD_VERSION=1

 ARG DEBIAN_FRONTEND=noninteractive
 ARG TARGETARCH
@@ -34,7 +34,6 @@ RUN wget --progress=dot:giga https://gcc.gnu.org/pub/gcc/releases/gcc-$GCC_VERSI
 WORKDIR /gcc-$GCC_VERSION
 RUN ./contrib/download_prerequisites

-# hadolint ignore=DL3059
 RUN mkdir /gcc-build
 WORKDIR /gcc-build
 RUN /gcc-$GCC_VERSION/configure \
--- a/docker/develop/compose.yaml
+++ b/docker/develop/compose.yaml
@@ -1,6 +1,6 @@
 services:
  clio_develop:
-    image: ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+    image: ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d
    volumes:
      - clio_develop_conan_data:/root/.conan2/p
      - clio_develop_ccache:/root/.ccache
--- a/docker/tools/Dockerfile
+++ b/docker/tools/Dockerfile
@@ -8,7 +8,7 @@ ARG TARGETARCH

 SHELL ["/bin/bash", "-o", "pipefail", "-c"]

-ARG BUILD_VERSION=0
+ARG BUILD_VERSION=2

 RUN apt-get update \
    && apt-get install -y --no-install-recommends --no-install-suggests \
@@ -24,7 +24,7 @@ RUN apt-get update \

 WORKDIR /tmp

-ARG MOLD_VERSION=2.40.4
+ARG MOLD_VERSION=2.40.1
 RUN wget --progress=dot:giga "https://github.com/rui314/mold/archive/refs/tags/v${MOLD_VERSION}.tar.gz" \
    && tar xf "v${MOLD_VERSION}.tar.gz" \
    && cd "mold-${MOLD_VERSION}" \
@@ -34,7 +34,7 @@ RUN wget --progress=dot:giga "https://github.com/rui314/mold/archive/refs/tags/v
    && ninja install \
    && rm -rf /tmp/* /var/tmp/*

-ARG CCACHE_VERSION=4.12.1
+ARG CCACHE_VERSION=4.11.3
 RUN wget --progress=dot:giga "https://github.com/ccache/ccache/releases/download/v${CCACHE_VERSION}/ccache-${CCACHE_VERSION}.tar.gz" \
    && tar xf "ccache-${CCACHE_VERSION}.tar.gz" \
    && cd "ccache-${CCACHE_VERSION}" \
@@ -51,7 +51,7 @@ RUN apt-get update \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/*

-ARG DOXYGEN_VERSION=1.15.0
+ARG DOXYGEN_VERSION=1.14.0
 RUN wget --progress=dot:giga "https://github.com/doxygen/doxygen/releases/download/Release_${DOXYGEN_VERSION//./_}/doxygen-${DOXYGEN_VERSION}.src.tar.gz" \
    && tar xf "doxygen-${DOXYGEN_VERSION}.src.tar.gz" \
    && cd "doxygen-${DOXYGEN_VERSION}" \
@@ -71,13 +71,13 @@ RUN wget --progress=dot:giga "https://github.com/aras-p/ClangBuildAnalyzer/archi
    && ninja install \
    && rm -rf /tmp/* /var/tmp/*

-ARG GIT_CLIFF_VERSION=2.10.1
+ARG GIT_CLIFF_VERSION=2.9.1
 RUN wget --progress=dot:giga "https://github.com/orhun/git-cliff/releases/download/v${GIT_CLIFF_VERSION}/git-cliff-${GIT_CLIFF_VERSION}-x86_64-unknown-linux-musl.tar.gz" \
    && tar xf git-cliff-${GIT_CLIFF_VERSION}-x86_64-unknown-linux-musl.tar.gz \
    && mv git-cliff-${GIT_CLIFF_VERSION}/git-cliff /usr/local/bin/git-cliff \
    && rm -rf /tmp/* /var/tmp/*

-ARG GH_VERSION=2.82.1
+ARG GH_VERSION=2.74.0
 RUN wget --progress=dot:giga "https://github.com/cli/cli/releases/download/v${GH_VERSION}/gh_${GH_VERSION}_linux_${TARGETARCH}.tar.gz" \
    && tar xf gh_${GH_VERSION}_linux_${TARGETARCH}.tar.gz \
    && mv gh_${GH_VERSION}_linux_${TARGETARCH}/bin/gh /usr/local/bin/gh \
--- a/docs/build-clio.md
+++ b/docs/build-clio.md
@@ -191,7 +191,7 @@ Open the `index.html` file in your browser to see the documentation pages.
 It is also possible to build Clio using [Docker](https://www.docker.com/) if you don't want to install all the dependencies on your machine.

 ```sh
-docker run -it ghcr.io/xrplf/clio-ci:62369411404eb32b0140603a785ff05e1dc36ce8
+docker run -it ghcr.io/xrplf/clio-ci:b2be4b51d1d81548ca48e2f2b8f67356b880c96d
 git clone https://github.com/XRPLF/clio
 cd clio
 ```
--- a/docs/config-description.md
+++ b/docs/config-description.md
@@ -293,7 +293,7 @@ This document provides a list of all available Clio configuration properties in

 - **Required**: True
 - **Type**: int
- **Default value**: `1000`
+- **Default value**: `1`
 - **Constraints**: The minimum value is `1`. The maximum value is `4294967295`.
 - **Description**: The maximum size of the server's request queue. If set to `0`, this means there is no queue size limit.

@@ -441,22 +441,6 @@ This document provides a list of all available Clio configuration properties in
 - **Constraints**: The value must be one of the following: `sync`, `async`, `none`.
 - **Description**: The strategy used for Cache loading.

-### cache.file.path
-
- **Required**: False
- **Type**: string
- **Default value**: None
- **Constraints**: None
- **Description**: The path to a file where cache will be saved to on shutdown and loaded from on startup. If the file couldn't be read Clio will load cache as usual (from DB or from rippled).
-
-### cache.file.max_sequence_age
-
- **Required**: True
- **Type**: int
- **Default value**: `5000`
- **Constraints**: None
- **Description**: Max allowed difference between the latest sequence in DB and in cache file. If the cache file is too old (contains too low latest sequence) Clio will reject using it.
-
 ### log.channels.[].channel

 - **Required**: False
--- a/docs/examples/config/example-config.json
+++ b/docs/examples/config/example-config.json
@@ -61,7 +61,7 @@
    "ip": "0.0.0.0",
    "port": 51233,
    // Max number of requests to queue up before rejecting further requests.
-    // Defaults to 1000 (use 0 to make the queue unbound).
+    // Defaults to 0, which disables the limit.
    "max_queue_size": 500,
    // If request contains header with authorization, Clio will check if it matches the prefix 'Password ' + this value's sha256 hash
    // If matches, the request will be considered as admin request
@@ -137,11 +137,7 @@
    // "num_cursors_from_account": 3200, // Read the cursors from the account table until we have enough cursors to partition the ledger to load concurrently.
    "num_markers": 48, // The number of markers is the number of coroutines to load the cache concurrently.
    "page_fetch_size": 512, // The number of rows to load for each page.
-    "load": "async", // "sync" to load cache synchronously  or "async" to load cache asynchronously or "none"/"no" to turn off the cache.
-    "file": {
-      "path": "./cache.bin",
-      "max_sequence_age": 5000
-    }
+    "load": "async" // "sync" to load cache synchronously  or "async" to load cache asynchronously or "none"/"no" to turn off the cache.
  },
  "prometheus": {
    "enabled": true,
--- a/pre-commit-hooks/json_in_cpp.py
+++ b/pre-commit-hooks/json_in_cpp.py
@@ -44,13 +44,8 @@ def fix_colon_spacing(cpp_content: str) -> str:


 def fix_indentation(cpp_content: str) -> str:
-    if "JSON(" not in cpp_content:
-        return cpp_content
-
    lines = cpp_content.splitlines()

-    ends_with_newline = cpp_content.endswith('\n')
-
    def find_indentation(line: str) -> int:
        return len(line) - len(line.lstrip())

@@ -71,11 +66,7 @@ def fix_indentation(cpp_content: str) -> str:
                        break
                    lines[i] = lines[i][by_how_much:] if by_how_much > 0 else " " * (-by_how_much) + lines[i]

-    result = "\n".join(lines)
-
-    if ends_with_newline:
-        result += "\n"
-    return result
+    return "\n".join(lines) + "\n"


 def process_file(file_path: Path, dry_run: bool) -> bool:
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -2,6 +2,7 @@ add_subdirectory(util)
 add_subdirectory(data)
 add_subdirectory(cluster)
 add_subdirectory(etl)
+add_subdirectory(etlng)
 add_subdirectory(feed)
 add_subdirectory(rpc)
 add_subdirectory(web)
--- a/src/app/CMakeLists.txt
+++ b/src/app/CMakeLists.txt
@@ -5,9 +5,10 @@ target_link_libraries(
  clio_app
  PUBLIC clio_cluster
         clio_etl
+         clio_etlng
         clio_feed
-         clio_migration
-         clio_rpc
         clio_web
+         clio_rpc
+         clio_migration
  PRIVATE Boost::program_options
 )
--- a/src/app/ClioApplication.cpp
+++ b/src/app/ClioApplication.cpp
@@ -28,6 +28,8 @@
 #include "etl/ETLService.hpp"
 #include "etl/LoadBalancer.hpp"
 #include "etl/NetworkValidatedLedgers.hpp"
+#include "etlng/LoadBalancer.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
 #include "feed/SubscriptionManager.hpp"
 #include "migration/MigrationInspectorFactory.hpp"
 #include "rpc/Counters.hpp"
@@ -55,7 +57,6 @@
 #include <cstdlib>
 #include <memory>
 #include <optional>
-#include <string>
 #include <thread>
 #include <utility>
 #include <vector>
@@ -102,7 +103,7 @@ ClioApplication::run(bool const useNgWebServer)
    // This is not the only io context in the application.
    boost::asio::io_context ioc{threads};

-    // Similarly we need a context to run ETL on
+    // Similarly we need a context to run ETLng on
    // In the future we can remove the raw ioc and use ctx instead
    util::async::CoroExecutionContext ctx{threads};

@@ -111,23 +112,7 @@ ClioApplication::run(bool const useNgWebServer)
    auto const dosguardWeights = web::dosguard::Weights::make(config_);
    auto dosGuard = web::dosguard::DOSGuard{config_, whitelistHandler, dosguardWeights};
    auto sweepHandler = web::dosguard::IntervalSweepHandler{config_, ioc, dosGuard};
-
    auto cache = data::LedgerCache{};
-    appStopper_.setOnStop([&cache, this](auto&&) {
-        // TODO(kuznetsss): move this into Stopper::makeOnStopCallback()
-        auto const cacheFilePath = config_.maybeValue<std::string>("cache.file.path");
-        if (not cacheFilePath.has_value()) {
-            return;
-        }
-
-        LOG(util::LogService::info()) << "Saving ledger cache to " << *cacheFilePath;
-        if (auto const [success, duration_ms] = util::timed([&]() { return cache.saveToFile(*cacheFilePath); });
-            success.has_value()) {
-            LOG(util::LogService::info()) << "Successfully saved ledger cache in " << duration_ms << " ms";
-        } else {
-            LOG(util::LogService::error()) << "Error saving LedgerCache to file";
-        }
-    });

    // Interface to the database
    auto backend = data::makeBackend(config_, cache);
@@ -157,12 +142,20 @@ ClioApplication::run(bool const useNgWebServer)
    // ETL uses the balancer to extract data.
    // The server uses the balancer to forward RPCs to a rippled node.
    // The balancer itself publishes to streams (transactions_proposed and accounts_proposed)
-    auto balancer = etl::LoadBalancer::makeLoadBalancer(
-        config_, ioc, backend, subscriptions, std::make_unique<util::MTRandomGenerator>(), ledgers
-    );
+    auto balancer = [&] -> std::shared_ptr<etlng::LoadBalancerInterface> {
+        if (config_.get<bool>("__ng_etl")) {
+            return etlng::LoadBalancer::makeLoadBalancer(
+                config_, ioc, backend, subscriptions, std::make_unique<util::MTRandomGenerator>(), ledgers
+            );
+        }
+
+        return etl::LoadBalancer::makeLoadBalancer(
+            config_, ioc, backend, subscriptions, std::make_unique<util::MTRandomGenerator>(), ledgers
+        );
+    }();

    // ETL is responsible for writing and publishing to streams. In read-only mode, ETL only publishes
-    auto etl = etl::ETLService::makeETLService(config_, ctx, backend, subscriptions, balancer, ledgers);
+    auto etl = etl::ETLService::makeETLService(config_, ioc, ctx, backend, subscriptions, balancer, ledgers);

    auto workQueue = rpc::WorkQueue::makeWorkQueue(config_);
    auto counters = rpc::Counters::makeCounters(workQueue);
--- a/src/app/Stopper.hpp
+++ b/src/app/Stopper.hpp
@@ -20,8 +20,8 @@
 #pragma once

 #include "data/BackendInterface.hpp"
-#include "etl/ETLServiceInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
+#include "etlng/ETLServiceInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "util/CoroutineGroup.hpp"
 #include "util/log/Logger.hpp"
@@ -78,8 +78,8 @@ public:
    static std::function<void(boost::asio::yield_context)>
    makeOnStopCallback(
        ServerType& server,
-        etl::LoadBalancerInterface& balancer,
-        etl::ETLServiceInterface& etl,
+        etlng::LoadBalancerInterface& balancer,
+        etlng::ETLServiceInterface& etl,
        feed::SubscriptionManagerInterface& subscriptions,
        data::BackendInterface& backend,
        boost::asio::io_context& ioc
--- a/src/data/AmendmentCenter.hpp
+++ b/src/data/AmendmentCenter.hpp
@@ -147,11 +147,6 @@ struct Amendments {
    REGISTER(fixAMMClawbackRounding);
    REGISTER(fixMPTDeliveredAmount);
    REGISTER(fixPriceOracleOrder);
-    REGISTER(DynamicMPT);
-    REGISTER(fixDelegateV1_1);
-    REGISTER(fixDirectoryLimit);
-    REGISTER(fixIncludeKeyletFields);
-    REGISTER(fixTokenEscrowV1);

    // Obsolete but supported by libxrpl
    REGISTER(CryptoConditionsSuite);
--- a/src/data/BackendInterface.cpp
+++ b/src/data/BackendInterface.cpp
@@ -270,7 +270,7 @@ BackendInterface::updateRange(uint32_t newMax)
 {
    std::scoped_lock const lck(rngMtx_);

-    if (range_.has_value() and newMax < range_->maxSequence) {
+    if (range_.has_value() && newMax < range_->maxSequence) {
        ASSERT(
            false,
            "Range shouldn't exist yet or newMax should be at least range->maxSequence. newMax = {}, "
@@ -280,14 +280,11 @@ BackendInterface::updateRange(uint32_t newMax)
        );
    }

-    updateRangeImpl(newMax);
-}
-
-void
-BackendInterface::forceUpdateRange(uint32_t newMax)
-{
-    std::scoped_lock const lck(rngMtx_);
-    updateRangeImpl(newMax);
+    if (!range_.has_value()) {
+        range_ = {.minSequence = newMax, .maxSequence = newMax};
+    } else {
+        range_->maxSequence = newMax;
+    }
 }

 void
@@ -413,14 +410,4 @@ BackendInterface::fetchFees(std::uint32_t const seq, boost::asio::yield_context
    return fees;
 }

-void
-BackendInterface::updateRangeImpl(uint32_t newMax)
-{
-    if (!range_.has_value()) {
-        range_ = {.minSequence = newMax, .maxSequence = newMax};
-    } else {
-        range_->maxSequence = newMax;
-    }
-}
-
 }  // namespace data
--- a/src/data/BackendInterface.hpp
+++ b/src/data/BackendInterface.hpp
@@ -249,15 +249,6 @@ public:
    void
    updateRange(uint32_t newMax);

-    /**
-     * @brief Updates the range of sequences that are stored in the DB without any checks
-     * @note In the most cases you should use updateRange() instead
-     *
-     * @param newMax The new maximum sequence available
-     */
-    void
-    forceUpdateRange(uint32_t newMax);
-
    /**
     * @brief Sets the range of sequences that are stored in the DB.
     *
@@ -785,9 +776,6 @@ private:
     */
    virtual bool
    doFinishWrites() = 0;
-
-    void
-    updateRangeImpl(uint32_t newMax);
 };

 }  // namespace data
--- a/src/data/CMakeLists.txt
+++ b/src/data/CMakeLists.txt
@@ -14,9 +14,6 @@ target_sources(
          cassandra/impl/SslContext.cpp
          cassandra/Handle.cpp
          cassandra/SettingsProvider.cpp
-          impl/InputFile.cpp
-          impl/LedgerCacheFile.cpp
-          impl/OutputFile.cpp
 )

 target_link_libraries(clio_data PUBLIC cassandra-cpp-driver::cassandra-cpp-driver clio_util)
--- a/src/data/LedgerCache.cpp
+++ b/src/data/LedgerCache.cpp
@@ -20,22 +20,16 @@
 #include "data/LedgerCache.hpp"

 #include "data/Types.hpp"
-#include "data/impl/LedgerCacheFile.hpp"
-#include "etl/Models.hpp"
+#include "etlng/Models.hpp"
 #include "util/Assert.hpp"

 #include <xrpl/basics/base_uint.h>

 #include <cstddef>
 #include <cstdint>
-#include <cstdlib>
-#include <cstring>
-#include <map>
 #include <mutex>
 #include <optional>
 #include <shared_mutex>
-#include <string>
-#include <utility>
 #include <vector>

 namespace data {
@@ -95,7 +89,7 @@ LedgerCache::update(std::vector<LedgerObject> const& objs, uint32_t seq, bool is
 }

 void
-LedgerCache::update(std::vector<etl::model::Object> const& objs, uint32_t seq)
+LedgerCache::update(std::vector<etlng::model::Object> const& objs, uint32_t seq)
 {
    if (disabled_)
        return;
@@ -257,34 +251,4 @@ LedgerCache::getSuccessorHitRate() const
    return static_cast<float>(successorHitCounter_.get().value()) / successorReqCounter_.get().value();
 }

-std::expected<void, std::string>
-LedgerCache::saveToFile(std::string const& path) const
-{
-    if (not isFull()) {
-        return std::unexpected{"Ledger cache is not full"};
-    }
-
-    impl::LedgerCacheFile file{path};
-    std::unique_lock const lock{mtx_};
-    impl::LedgerCacheFile::DataView const data{.latestSeq = latestSeq_, .map = map_, .deleted = deleted_};
-    return file.write(data);
-}
-
-std::expected<void, std::string>
-LedgerCache::loadFromFile(std::string const& path, uint32_t minLatestSequence)
-{
-    impl::LedgerCacheFile file{path};
-    auto data = file.read(minLatestSequence);
-    if (not data.has_value()) {
-        return std::unexpected(std::move(data).error());
-    }
-    auto [latestSeq, map, deleted] = std::move(data).value();
-    std::unique_lock const lock{mtx_};
-    latestSeq_ = latestSeq;
-    map_ = std::move(map);
-    deleted_ = std::move(deleted);
-    full_ = true;
-    return {};
-}
-
 }  // namespace data
--- a/src/data/LedgerCache.hpp
+++ b/src/data/LedgerCache.hpp
@@ -21,7 +21,7 @@

 #include "data/LedgerCacheInterface.hpp"
 #include "data/Types.hpp"
-#include "etl/Models.hpp"
+#include "etlng/Models.hpp"
 #include "util/prometheus/Bool.hpp"
 #include "util/prometheus/Counter.hpp"
 #include "util/prometheus/Label.hpp"
@@ -37,7 +37,6 @@
 #include <map>
 #include <optional>
 #include <shared_mutex>
-#include <string>
 #include <unordered_set>
 #include <vector>

@@ -47,16 +46,11 @@ namespace data {
 * @brief Cache for an entire ledger.
 */
 class LedgerCache : public LedgerCacheInterface {
-public:
-    /** @brief An entry of the cache */
    struct CacheEntry {
        uint32_t seq = 0;
        Blob blob;
    };

-    using CacheMap = std::map<ripple::uint256, CacheEntry>;
-
-private:
    // counters for fetchLedgerObject(s) hit rate
    std::reference_wrapper<util::prometheus::CounterInt> objectReqCounter_{PrometheusService::counterInt(
        "ledger_cache_counter_total_number",
@@ -79,8 +73,8 @@ private:
        util::prometheus::Labels({{"type", "cache_hit"}, {"fetch", "successor_key"}})
    )};

-    CacheMap map_;
-    CacheMap deleted_;
+    std::map<ripple::uint256, CacheEntry> map_;
+    std::map<ripple::uint256, CacheEntry> deleted_;

    mutable std::shared_mutex mtx_;
    std::condition_variable_any cv_;
@@ -104,7 +98,7 @@ public:
    update(std::vector<LedgerObject> const& objs, uint32_t seq, bool isBackground) override;

    void
-    update(std::vector<etl::model::Object> const& objs, uint32_t seq) override;
+    update(std::vector<etlng::model::Object> const& objs, uint32_t seq) override;

    std::optional<Blob>
    get(ripple::uint256 const& key, uint32_t seq) const override;
@@ -144,19 +138,6 @@ public:

    void
    waitUntilCacheContainsSeq(uint32_t seq) override;
-
-    /**
-     * @brief Save the cache to file
-     * @note This operation takes about 7 seconds and it keeps mtx_ exclusively locked
-     *
-     * @param path The file path to save the cache to
-     * @return An error as a string if any
-     */
-    std::expected<void, std::string>
-    saveToFile(std::string const& path) const;
-
-    std::expected<void, std::string>
-    loadFromFile(std::string const& path, uint32_t minLatestSequence) override;
 };

 }  // namespace data
--- a/src/data/LedgerCacheInterface.hpp
+++ b/src/data/LedgerCacheInterface.hpp
@@ -20,16 +20,14 @@
 #pragma once

 #include "data/Types.hpp"
-#include "etl/Models.hpp"
+#include "etlng/Models.hpp"

 #include <xrpl/basics/base_uint.h>
 #include <xrpl/basics/hardened_hash.h>

 #include <cstddef>
 #include <cstdint>
-#include <expected>
 #include <optional>
-#include <string>
 #include <vector>

 namespace data {
@@ -65,7 +63,7 @@ public:
     * @param seq The sequence to update cache for
     */
    virtual void
-    update(std::vector<etl::model::Object> const& objs, uint32_t seq) = 0;
+    update(std::vector<etlng::model::Object> const& objs, uint32_t seq) = 0;

    /**
     * @brief Fetch a cached object by its key and sequence number.
@@ -170,17 +168,6 @@ public:
     */
    virtual void
    waitUntilCacheContainsSeq(uint32_t seq) = 0;
-
-    /**
-     * @brief Load the cache from file
-     * @note This operation takes about 7 seconds and it keeps mtx_ exclusively locked
-     *
-     * @param path The file path to load data from
-     * @param minLatestSequence The minimum allowed value of the latestLedgerSequence in cache file
-     * @return An error as a string if any
-     */
-    [[nodiscard]] virtual std::expected<void, std::string>
-    loadFromFile(std::string const& path, uint32_t minLatestSequence) = 0;
 };

 }  // namespace data
--- a/src/data/Types.hpp
+++ b/src/data/Types.hpp
@@ -247,9 +247,6 @@ struct MPTHoldersAndCursor {
 struct LedgerRange {
    std::uint32_t minSequence = 0;
    std::uint32_t maxSequence = 0;
-
-    bool
-    operator==(LedgerRange const&) const = default;
 };

 /**
--- a/src/data/impl/InputFile.cpp
+++ b/src/data/impl/InputFile.cpp
@@ -1,58 +0,0 @@
-//------------------------------------------------------------------------------
-/*
-    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
-
-    Permission to use, copy, modify, and distribute this software for any
-    purpose with or without fee is hereby granted, provided that the above
-    copyright notice and this permission notice appear in all copies.
-
-    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
-    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
-    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-*/
-//==============================================================================
-
-#include "data/impl/InputFile.hpp"
-
-#include <xrpl/basics/base_uint.h>
-
-#include <cstddef>
-#include <cstring>
-#include <ios>
-#include <iosfwd>
-#include <string>
-#include <utility>
-
-namespace data::impl {
-
-InputFile::InputFile(std::string const& path) : file_(path, std::ios::binary | std::ios::in)
-{
-}
-
-bool
-InputFile::isOpen() const
-{
-    return file_.is_open();
-}
-
-bool
-InputFile::readRaw(char* data, size_t size)
-{
-    file_.read(data, size);
-    shasum_.update(data, size);
-    return not file_.fail();
-}
-
-ripple::uint256
-InputFile::hash() const
-{
-    auto sum = shasum_;
-    return std::move(sum).finalize();
-}
-
-}  // namespace data::impl
--- a/src/data/impl/LedgerCacheFile.cpp
+++ b/src/data/impl/LedgerCacheFile.cpp
@@ -1,210 +0,0 @@
-//------------------------------------------------------------------------------
-/*
-    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
-
-    Permission to use, copy, modify, and distribute this software for any
-    purpose with or without fee is hereby granted, provided that the above
-    copyright notice and this permission notice appear in all copies.
-
-    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
-    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
-    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-*/
-//==============================================================================
-
-#include "data/impl/LedgerCacheFile.hpp"
-
-#include "data/LedgerCache.hpp"
-#include "data/Types.hpp"
-
-#include <fmt/format.h>
-#include <xrpl/basics/base_uint.h>
-
-#include <algorithm>
-#include <array>
-#include <cstddef>
-#include <cstdint>
-#include <exception>
-#include <filesystem>
-#include <string>
-#include <utility>
-
-namespace data::impl {
-
-using Hash = ripple::uint256;
-using Separator = std::array<char, 16>;
-static constexpr Separator kSEPARATOR = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
-
-namespace {
-
-std::expected<std::pair<ripple::uint256, LedgerCache::CacheEntry>, std::string>
-readCacheEntry(InputFile& file, size_t i)
-{
-    ripple::uint256 key;
-    if (not file.readRaw(reinterpret_cast<char*>(key.data()), ripple::base_uint<256>::bytes)) {
-        return std::unexpected(fmt::format("Failed to read key at index {}", i));
-    }
-
-    uint32_t seq{};
-    if (not file.read(seq)) {
-        return std::unexpected(fmt::format("Failed to read sequence at index {}", i));
-    }
-
-    size_t blobSize{};
-    if (not file.read(blobSize)) {
-        return std::unexpected(fmt::format("Failed to read blob size at index {}", i));
-    }
-
-    Blob blob(blobSize);
-    if (not file.readRaw(reinterpret_cast<char*>(blob.data()), blobSize)) {
-        return std::unexpected(fmt::format("Failed to read blob data at index {}", i));
-    }
-    return std::make_pair(key, LedgerCache::CacheEntry{.seq = seq, .blob = std::move(blob)});
-}
-
-std::expected<void, std::string>
-verifySeparator(Separator const& s)
-{
-    if (not std::ranges::all_of(s, [](char c) { return c == 0; })) {
-        return std::unexpected{"Separator verification failed - data corruption detected"};
-    }
-    return {};
-}
-
-}  // anonymous namespace
-
-LedgerCacheFile::LedgerCacheFile(std::string path) : path_(std::move(path))
-{
-}
-
-std::expected<void, std::string>
-LedgerCacheFile::write(DataView dataView)
-{
-    auto const newFilePath = fmt::format("{}.new", path_);
-    auto file = OutputFile{newFilePath};
-    if (not file.isOpen()) {
-        return std::unexpected{fmt::format("Couldn't open file: {}", newFilePath)};
-    }
-
-    Header const header{
-        .latestSeq = dataView.latestSeq, .mapSize = dataView.map.size(), .deletedSize = dataView.deleted.size()
-    };
-    file.write(header);
-    file.write(kSEPARATOR);
-
-    for (auto const& [k, v] : dataView.map) {
-        file.write(k.data(), decltype(k)::bytes);
-        file.write(v.seq);
-        file.write(v.blob.size());
-        file.writeRaw(reinterpret_cast<char const*>(v.blob.data()), v.blob.size());
-    }
-    file.write(kSEPARATOR);
-
-    for (auto const& [k, v] : dataView.deleted) {
-        file.write(k.data(), decltype(k)::bytes);
-        file.write(v.seq);
-        file.write(v.blob.size());
-        file.writeRaw(reinterpret_cast<char const*>(v.blob.data()), v.blob.size());
-    }
-    file.write(kSEPARATOR);
-    auto const hash = file.hash();
-    file.write(hash.data(), decltype(hash)::bytes);
-
-    try {
-        std::filesystem::rename(newFilePath, path_);
-    } catch (std::exception const& e) {
-        return std::unexpected{fmt::format("Error moving cache file from {} to {}: {}", newFilePath, path_, e.what())};
-    }
-
-    return {};
-}
-
-std::expected<LedgerCacheFile::Data, std::string>
-LedgerCacheFile::read(uint32_t minLatestSequence)
-{
-    try {
-        auto file = InputFile{path_};
-        if (not file.isOpen()) {
-            return std::unexpected{fmt::format("Couldn't open file: {}", path_)};
-        }
-
-        Data result;
-
-        Header header{};
-        if (not file.read(header)) {
-            return std::unexpected{"Error reading cache header"};
-        }
-        if (header.version != kVERSION) {
-            return std::unexpected{
-                fmt::format("Cache has wrong version: expected {} found {}", kVERSION, header.version)
-            };
-        }
-        if (header.latestSeq < minLatestSequence) {
-            return std::unexpected{fmt::format("Latest sequence ({}) in the cache file is too low.", header.latestSeq)};
-        }
-        result.latestSeq = header.latestSeq;
-
-        Separator separator{};
-        if (not file.readRaw(separator.data(), separator.size())) {
-            return std::unexpected{"Error reading cache header"};
-        }
-        if (auto verificationResult = verifySeparator(separator); not verificationResult.has_value()) {
-            return std::unexpected{std::move(verificationResult).error()};
-        }
-
-        for (size_t i = 0; i < header.mapSize; ++i) {
-            auto cacheEntryExpected = readCacheEntry(file, i);
-            if (not cacheEntryExpected.has_value()) {
-                return std::unexpected{std::move(cacheEntryExpected).error()};
-            }
-            // Using insert with hint here to decrease insert operation complexity to the amortized constant instead of
-            // logN
-            result.map.insert(result.map.end(), std::move(cacheEntryExpected).value());
-        }
-
-        if (not file.readRaw(separator.data(), separator.size())) {
-            return std::unexpected{"Error reading separator"};
-        }
-        if (auto verificationResult = verifySeparator(separator); not verificationResult.has_value()) {
-            return std::unexpected{std::move(verificationResult).error()};
-        }
-
-        for (size_t i = 0; i < header.deletedSize; ++i) {
-            auto cacheEntryExpected = readCacheEntry(file, i);
-            if (not cacheEntryExpected.has_value()) {
-                return std::unexpected{std::move(cacheEntryExpected).error()};
-            }
-            result.deleted.insert(result.deleted.end(), std::move(cacheEntryExpected).value());
-        }
-
-        if (not file.readRaw(separator.data(), separator.size())) {
-            return std::unexpected{"Error reading separator"};
-        }
-        if (auto verificationResult = verifySeparator(separator); not verificationResult.has_value()) {
-            return std::unexpected{std::move(verificationResult).error()};
-        }
-
-        auto const dataHash = file.hash();
-        ripple::uint256 hashFromFile{};
-        if (not file.readRaw(reinterpret_cast<char*>(hashFromFile.data()), decltype(hashFromFile)::bytes)) {
-            return std::unexpected{"Error reading hash"};
-        }
-
-        if (dataHash != hashFromFile) {
-            return std::unexpected{"Hash file corruption detected"};
-        }
-
-        return result;
-    } catch (std::exception const& e) {
-        return std::unexpected{fmt::format(" Error reading cache file: {}", e.what())};
-    } catch (...) {
-        return std::unexpected{fmt::format(" Error reading cache file")};
-    }
-}
-
-}  // namespace data::impl
--- a/src/data/impl/LedgerCacheFile.hpp
+++ b/src/data/impl/LedgerCacheFile.hpp
@@ -1,70 +0,0 @@
-//------------------------------------------------------------------------------
-/*
-    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
-
-    Permission to use, copy, modify, and distribute this software for any
-    purpose with or without fee is hereby granted, provided that the above
-    copyright notice and this permission notice appear in all copies.
-
-    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
-    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
-    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-*/
-//==============================================================================
-
-#pragma once
-
-#include "data/LedgerCache.hpp"
-#include "data/impl/InputFile.hpp"
-#include "data/impl/OutputFile.hpp"
-
-#include <fmt/format.h>
-#include <xrpl/basics/base_uint.h>
-
-#include <cstddef>
-#include <cstdint>
-#include <cstring>
-#include <string>
-
-namespace data::impl {
-
-class LedgerCacheFile {
-public:
-    struct Header {
-        uint32_t version = kVERSION;
-        uint32_t latestSeq{};
-        uint64_t mapSize{};
-        uint64_t deletedSize{};
-    };
-
-private:
-    static constexpr uint32_t kVERSION = 1;
-
-    std::string path_;
-
-public:
-    template <typename T>
-    struct DataBase {
-        uint32_t latestSeq{0};
-        T map;
-        T deleted;
-    };
-
-    using DataView = DataBase<LedgerCache::CacheMap const&>;
-    using Data = DataBase<LedgerCache::CacheMap>;
-
-    LedgerCacheFile(std::string path);
-
-    std::expected<void, std::string>
-    write(DataView dataView);
-
-    std::expected<Data, std::string>
-    read(uint32_t minLatestSequence);
-};
-
-}  // namespace data::impl
--- a/src/data/impl/OutputFile.cpp
+++ b/src/data/impl/OutputFile.cpp
@@ -1,62 +0,0 @@
-//------------------------------------------------------------------------------
-/*
-    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
-
-    Permission to use, copy, modify, and distribute this software for any
-    purpose with or without fee is hereby granted, provided that the above
-    copyright notice and this permission notice appear in all copies.
-
-    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
-    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
-    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-*/
-//==============================================================================
-
-#include "data/impl/OutputFile.hpp"
-
-#include <xrpl/basics/base_uint.h>
-
-#include <cstddef>
-#include <cstring>
-#include <ios>
-#include <string>
-#include <utility>
-
-namespace data::impl {
-
-OutputFile::OutputFile(std::string const& path) : file_(path, std::ios::binary | std::ios::out)
-{
-}
-
-bool
-OutputFile::isOpen() const
-{
-    return file_.is_open();
-}
-
-void
-OutputFile::writeRaw(char const* data, size_t size)
-{
-    writeToFile(data, size);
-}
-
-void
-OutputFile::writeToFile(char const* data, size_t size)
-{
-    file_.write(data, size);
-    shasum_.update(data, size);
-}
-
-ripple::uint256
-OutputFile::hash() const
-{
-    auto sum = shasum_;
-    return std::move(sum).finalize();
-}
-
-}  // namespace data::impl
--- a/src/data/impl/OutputFile.hpp
+++ b/src/data/impl/OutputFile.hpp
@@ -1,68 +0,0 @@
-//------------------------------------------------------------------------------
-/*
-    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
-
-    Permission to use, copy, modify, and distribute this software for any
-    purpose with or without fee is hereby granted, provided that the above
-    copyright notice and this permission notice appear in all copies.
-
-    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
-    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
-    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-*/
-//==============================================================================
-
-#pragma once
-
-#include "util/Shasum.hpp"
-
-#include <xrpl/basics/base_uint.h>
-
-#include <cstddef>
-#include <cstring>
-#include <fstream>
-#include <string>
-
-namespace data::impl {
-
-class OutputFile {
-    std::ofstream file_;
-    util::Sha256sum shasum_;
-
-public:
-    OutputFile(std::string const& path);
-
-    bool
-    isOpen() const;
-
-    template <typename T>
-    void
-    write(T&& data)
-    {
-        writeRaw(reinterpret_cast<char const*>(&data), sizeof(T));
-    }
-
-    template <typename T>
-    void
-    write(T const* data, size_t const size)
-    {
-        writeRaw(reinterpret_cast<char const*>(data), size);
-    }
-
-    void
-    writeRaw(char const* data, size_t size);
-
-    ripple::uint256
-    hash() const;
-
-private:
-    void
-    writeToFile(char const* data, size_t size);
-};
-
-}  // namespace data::impl
--- a/src/etl/CMakeLists.txt
+++ b/src/etl/CMakeLists.txt
@@ -7,24 +7,14 @@ target_sources(
          ETLService.cpp
          ETLState.cpp
          LoadBalancer.cpp
-          MPTHelpers.cpp
          NetworkValidatedLedgers.cpp
          NFTHelpers.cpp
          Source.cpp
+          MPTHelpers.cpp
          impl/AmendmentBlockHandler.cpp
-          impl/AsyncGrpcCall.cpp
-          impl/Extraction.cpp
          impl/ForwardingSource.cpp
          impl/GrpcSource.cpp
-          impl/Loading.cpp
-          impl/Monitor.cpp
          impl/SubscriptionSource.cpp
-          impl/TaskManager.cpp
-          impl/ext/Cache.cpp
-          impl/ext/Core.cpp
-          impl/ext/MPT.cpp
-          impl/ext/NFT.cpp
-          impl/ext/Successor.cpp
 )

 target_link_libraries(clio_etl PUBLIC clio_data)
--- a/src/etl/CacheLoader.hpp
+++ b/src/etl/CacheLoader.hpp
@@ -21,20 +21,16 @@

 #include "data/BackendInterface.hpp"
 #include "data/LedgerCacheInterface.hpp"
-#include "data/Types.hpp"
-#include "etl/CacheLoaderInterface.hpp"
 #include "etl/CacheLoaderSettings.hpp"
 #include "etl/impl/CacheLoader.hpp"
 #include "etl/impl/CursorFromAccountProvider.hpp"
 #include "etl/impl/CursorFromDiffProvider.hpp"
 #include "etl/impl/CursorFromFixDiffNumProvider.hpp"
+#include "etlng/CacheLoaderInterface.hpp"
 #include "util/Assert.hpp"
-#include "util/Profiler.hpp"
 #include "util/async/context/BasicExecutionContext.hpp"
-#include "util/config/ConfigDefinition.hpp"
 #include "util/log/Logger.hpp"

-#include <algorithm>
 #include <cstdint>
 #include <functional>
 #include <memory>
@@ -52,7 +48,7 @@ namespace etl {
 * @tparam ExecutionContextType The type of the execution context to use
 */
 template <typename ExecutionContextType = util::async::CoroExecutionContext>
-class CacheLoader : public CacheLoaderInterface {
+class CacheLoader : public etlng::CacheLoaderInterface {
    using CacheLoaderType = impl::CacheLoaderImpl<data::LedgerCacheInterface>;

    util::Logger log_{"ETL"};
@@ -102,10 +98,6 @@ public:
            return;
        }

-        if (loadCacheFromFile()) {
-            return;
-        }
-
        std::shared_ptr<impl::BaseCursorProvider> provider;
        if (settings_.numCacheCursorsFromDiff != 0) {
            LOG(log_.info()) << "Loading cache with cursor from num_cursors_from_diff="
@@ -157,36 +149,6 @@ public:
        if (loader_ != nullptr)
            loader_->wait();
    }
-
-private:
-    bool
-    loadCacheFromFile()
-    {
-        if (not settings_.cacheFileSettings.has_value()) {
-            return false;
-        }
-        LOG(log_.info()) << "Loading ledger cache from " << settings_.cacheFileSettings->path;
-        auto const minLatestSequence =
-            backend_->fetchLedgerRange()
-                .transform([this](data::LedgerRange const& range) {
-                    return std::max(range.maxSequence - settings_.cacheFileSettings->maxAge, range.minSequence);
-                })
-                .value_or(0);
-
-        auto const [success, duration_ms] = util::timed([&]() {
-            return cache_.get().loadFromFile(settings_.cacheFileSettings->path, minLatestSequence);
-        });
-
-        if (not success.has_value()) {
-            LOG(log_.warn()) << "Error loading cache from file: " << success.error();
-            return false;
-        }
-
-        LOG(log_.info()) << "Loaded cache from file in " << duration_ms
-                         << " ms. Latest sequence: " << cache_.get().latestLedgerSequence();
-        backend_->forceUpdateRange(cache_.get().latestLedgerSequence());
-        return true;
-    }
 };

 }  // namespace etl
--- a/src/etl/CacheLoaderSettings.cpp
+++ b/src/etl/CacheLoaderSettings.cpp
@@ -26,7 +26,6 @@
 #include <cstddef>
 #include <cstdint>
 #include <string>
-#include <utility>

 namespace etl {

@@ -64,12 +63,6 @@ makeCacheLoaderSettings(util::config::ClioConfigDefinition const& config)
    settings.numCacheMarkers = cache.get<std::size_t>("num_markers");
    settings.cachePageFetchSize = cache.get<std::size_t>("page_fetch_size");

-    if (auto filePath = cache.maybeValue<std::string>("file.path"); filePath.has_value()) {
-        settings.cacheFileSettings = CacheLoaderSettings::CacheFileSettings{
-            .path = std::move(filePath).value(), .maxAge = cache.get<uint32_t>("file.max_sequence_age")
-        };
-    }
-
    auto const entry = cache.get<std::string>("load");
    if (boost::iequals(entry, "sync"))
        settings.loadStyle = CacheLoaderSettings::LoadStyle::SYNC;
--- a/src/etl/CacheLoaderSettings.hpp
+++ b/src/etl/CacheLoaderSettings.hpp
@@ -22,9 +22,6 @@
 #include "util/config/ConfigDefinition.hpp"

 #include <cstddef>
-#include <cstdint>
-#include <optional>
-#include <string>

 namespace etl {

@@ -35,15 +32,6 @@ struct CacheLoaderSettings {
    /** @brief Ways to load the cache */
    enum class LoadStyle { ASYNC, SYNC, NONE };

-    /** @brief Settings for cache file operations */
-    struct CacheFileSettings {
-        std::string path;       /**< path to the file to load cache from on start and save cache to on shutdown */
-        uint32_t maxAge = 5000; /**< max difference between latest sequence in cache file and DB */
-
-        auto
-        operator<=>(CacheFileSettings const&) const = default;
-    };
-
    size_t numCacheDiffs = 32;             /**< number of diffs to use to generate cursors */
    size_t numCacheMarkers = 48;           /**< number of markers to use at one time to traverse the ledger */
    size_t cachePageFetchSize = 512;       /**< number of ledger objects to fetch concurrently per marker */
@@ -51,8 +39,7 @@ struct CacheLoaderSettings {
    size_t numCacheCursorsFromDiff = 0;    /**< number of cursors to fetch from diff */
    size_t numCacheCursorsFromAccount = 0; /**< number of cursors to fetch from account_tx */

-    LoadStyle loadStyle = LoadStyle::ASYNC;             /**< how to load the cache */
-    std::optional<CacheFileSettings> cacheFileSettings; /**< optional settings for cache file operations */
+    LoadStyle loadStyle = LoadStyle::ASYNC; /**< how to load the cache */

    auto
    operator<=>(CacheLoaderSettings const&) const = default;
--- a/src/etl/ETLService.cpp
+++ b/src/etl/ETLService.cpp
@@ -1,7 +1,7 @@
 //------------------------------------------------------------------------------
 /*
    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
+    Copyright (c) 2023, the clio developers.

    Permission to use, copy, modify, and distribute this software for any
    purpose with or without fee is hereby granted, provided that the above
@@ -20,392 +20,371 @@
 #include "etl/ETLService.hpp"

 #include "data/BackendInterface.hpp"
-#include "data/LedgerCacheInterface.hpp"
-#include "data/Types.hpp"
 #include "etl/CacheLoader.hpp"
-#include "etl/CacheLoaderInterface.hpp"
-#include "etl/CacheUpdaterInterface.hpp"
 #include "etl/CorruptionDetector.hpp"
-#include "etl/ETLServiceInterface.hpp"
-#include "etl/ETLState.hpp"
-#include "etl/ExtractorInterface.hpp"
-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LedgerPublisherInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
-#include "etl/LoaderInterface.hpp"
-#include "etl/MonitorInterface.hpp"
-#include "etl/MonitorProviderInterface.hpp"
+#include "etl/LoadBalancer.hpp"
 #include "etl/NetworkValidatedLedgersInterface.hpp"
 #include "etl/SystemState.hpp"
-#include "etl/TaskManagerProviderInterface.hpp"
 #include "etl/impl/AmendmentBlockHandler.hpp"
-#include "etl/impl/CacheUpdater.hpp"
-#include "etl/impl/Extraction.hpp"
+#include "etl/impl/ExtractionDataPipe.hpp"
+#include "etl/impl/Extractor.hpp"
 #include "etl/impl/LedgerFetcher.hpp"
+#include "etl/impl/LedgerLoader.hpp"
 #include "etl/impl/LedgerPublisher.hpp"
-#include "etl/impl/Loading.hpp"
-#include "etl/impl/MonitorProvider.hpp"
-#include "etl/impl/Registry.hpp"
-#include "etl/impl/Scheduling.hpp"
-#include "etl/impl/TaskManager.hpp"
-#include "etl/impl/TaskManagerProvider.hpp"
-#include "etl/impl/ext/Cache.hpp"
-#include "etl/impl/ext/Core.hpp"
-#include "etl/impl/ext/MPT.hpp"
-#include "etl/impl/ext/NFT.hpp"
-#include "etl/impl/ext/Successor.hpp"
+#include "etl/impl/Transformer.hpp"
+#include "etlng/ETLService.hpp"
+#include "etlng/ETLServiceInterface.hpp"
+#include "etlng/LoadBalancer.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
+#include "etlng/impl/LedgerPublisher.hpp"
+#include "etlng/impl/MonitorProvider.hpp"
+#include "etlng/impl/TaskManagerProvider.hpp"
+#include "etlng/impl/ext/Cache.hpp"
+#include "etlng/impl/ext/Core.hpp"
+#include "etlng/impl/ext/MPT.hpp"
+#include "etlng/impl/ext/NFT.hpp"
+#include "etlng/impl/ext/Successor.hpp"
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "util/Assert.hpp"
-#include "util/Profiler.hpp"
+#include "util/Constants.hpp"
 #include "util/async/AnyExecutionContext.hpp"
+#include "util/config/ConfigDefinition.hpp"
 #include "util/log/Logger.hpp"

-#include <boost/json/object.hpp>
-#include <boost/signals2/connection.hpp>
+#include <boost/asio/io_context.hpp>
+#include <xrpl/beast/core/CurrentThreadName.h>
 #include <xrpl/protocol/LedgerHeader.h>

 #include <chrono>
 #include <cstddef>
 #include <cstdint>
-#include <functional>
 #include <memory>
 #include <optional>
-#include <string>
+#include <stdexcept>
+#include <thread>
 #include <utility>
+#include <vector>

 namespace etl {

-std::shared_ptr<ETLServiceInterface>
+std::shared_ptr<etlng::ETLServiceInterface>
 ETLService::makeETLService(
    util::config::ClioConfigDefinition const& config,
+    boost::asio::io_context& ioc,
    util::async::AnyExecutionContext ctx,
    std::shared_ptr<BackendInterface> backend,
    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
-    std::shared_ptr<LoadBalancerInterface> balancer,
+    std::shared_ptr<etlng::LoadBalancerInterface> balancer,
    std::shared_ptr<NetworkValidatedLedgersInterface> ledgers
 )
 {
-    std::shared_ptr<ETLServiceInterface> ret;
+    std::shared_ptr<etlng::ETLServiceInterface> ret;

-    auto state = std::make_shared<SystemState>();
-    state->isStrictReadonly = config.get<bool>("read_only");
+    if (config.get<bool>("__ng_etl")) {
+        ASSERT(
+            std::dynamic_pointer_cast<etlng::LoadBalancer>(balancer), "LoadBalancer type must be etlng::LoadBalancer"
+        );

-    auto fetcher = std::make_shared<impl::LedgerFetcher>(backend, balancer);
-    auto extractor = std::make_shared<impl::Extractor>(fetcher);
-    auto publisher = std::make_shared<impl::LedgerPublisher>(ctx, backend, subscriptions, *state);
-    auto cacheLoader = std::make_shared<CacheLoader<>>(config, backend, backend->cache());
-    auto cacheUpdater = std::make_shared<impl::CacheUpdater>(backend->cache());
-    auto amendmentBlockHandler = std::make_shared<impl::AmendmentBlockHandler>(ctx, *state);
-    auto monitorProvider = std::make_shared<impl::MonitorProvider>();
+        auto state = std::make_shared<etl::SystemState>();
+        state->isStrictReadonly = config.get<bool>("read_only");

-    backend->setCorruptionDetector(CorruptionDetector{*state, backend->cache()});
+        auto fetcher = std::make_shared<etl::impl::LedgerFetcher>(backend, balancer);
+        auto extractor = std::make_shared<etlng::impl::Extractor>(fetcher);
+        auto publisher = std::make_shared<etlng::impl::LedgerPublisher>(ioc, backend, subscriptions, *state);
+        auto cacheLoader = std::make_shared<etl::CacheLoader<>>(config, backend, backend->cache());
+        auto cacheUpdater = std::make_shared<etlng::impl::CacheUpdater>(backend->cache());
+        auto amendmentBlockHandler = std::make_shared<etlng::impl::AmendmentBlockHandler>(ctx, *state);
+        auto monitorProvider = std::make_shared<etlng::impl::MonitorProvider>();

-    auto loader = std::make_shared<impl::Loader>(
-        backend,
-        impl::makeRegistry(
-            *state,
-            impl::CacheExt{cacheUpdater},
-            impl::CoreExt{backend},
-            impl::SuccessorExt{backend, backend->cache()},
-            impl::NFTExt{backend},
-            impl::MPTExt{backend}
-        ),
-        amendmentBlockHandler,
-        state
-    );
+        backend->setCorruptionDetector(CorruptionDetector{*state, backend->cache()});

-    auto taskManagerProvider = std::make_shared<impl::TaskManagerProvider>(*ledgers, extractor, loader);
+        auto loader = std::make_shared<etlng::impl::Loader>(
+            backend,
+            etlng::impl::makeRegistry(
+                *state,
+                etlng::impl::CacheExt{cacheUpdater},
+                etlng::impl::CoreExt{backend},
+                etlng::impl::SuccessorExt{backend, backend->cache()},
+                etlng::impl::NFTExt{backend},
+                etlng::impl::MPTExt{backend}
+            ),
+            amendmentBlockHandler,
+            state
+        );

-    ret = std::make_shared<ETLService>(
-        ctx,
-        config,
-        backend,
-        balancer,
-        ledgers,
-        publisher,
-        cacheLoader,
-        cacheUpdater,
-        extractor,
-        loader,  // loader itself
-        loader,  // initial load observer
-        taskManagerProvider,
-        monitorProvider,
-        state
-    );
+        auto taskManagerProvider = std::make_shared<etlng::impl::TaskManagerProvider>(*ledgers, extractor, loader);
+
+        ret = std::make_shared<etlng::ETLService>(
+            ctx,
+            config,
+            backend,
+            balancer,
+            ledgers,
+            publisher,
+            cacheLoader,
+            cacheUpdater,
+            extractor,
+            loader,  // loader itself
+            loader,  // initial load observer
+            taskManagerProvider,
+            monitorProvider,
+            state
+        );
+    } else {
+        ASSERT(std::dynamic_pointer_cast<etl::LoadBalancer>(balancer), "LoadBalancer type must be etl::LoadBalancer");
+        ret = std::make_shared<etl::ETLService>(config, ioc, backend, subscriptions, balancer, ledgers);
+    }

    // inject networkID into subscriptions, as transaction feed require it to inject CTID in response
-    if (auto const etlState = ret->getETLState(); etlState)
-        subscriptions->setNetworkID(etlState->networkID);
+    if (auto const state = ret->getETLState(); state)
+        subscriptions->setNetworkID(state->networkID);

    ret->run();
    return ret;
 }

-ETLService::ETLService(
-    util::async::AnyExecutionContext ctx,
-    std::reference_wrapper<util::config::ClioConfigDefinition const> config,
-    std::shared_ptr<data::BackendInterface> backend,
-    std::shared_ptr<LoadBalancerInterface> balancer,
-    std::shared_ptr<NetworkValidatedLedgersInterface> ledgers,
-    std::shared_ptr<LedgerPublisherInterface> publisher,
-    std::shared_ptr<CacheLoaderInterface> cacheLoader,
-    std::shared_ptr<CacheUpdaterInterface> cacheUpdater,
-    std::shared_ptr<ExtractorInterface> extractor,
-    std::shared_ptr<LoaderInterface> loader,
-    std::shared_ptr<InitialLoadObserverInterface> initialLoadObserver,
-    std::shared_ptr<TaskManagerProviderInterface> taskManagerProvider,
-    std::shared_ptr<MonitorProviderInterface> monitorProvider,
-    std::shared_ptr<SystemState> state
-)
-    : ctx_(std::move(ctx))
-    , config_(config)
-    , backend_(std::move(backend))
-    , balancer_(std::move(balancer))
-    , ledgers_(std::move(ledgers))
-    , publisher_(std::move(publisher))
-    , cacheLoader_(std::move(cacheLoader))
-    , cacheUpdater_(std::move(cacheUpdater))
-    , extractor_(std::move(extractor))
-    , loader_(std::move(loader))
-    , initialLoadObserver_(std::move(initialLoadObserver))
-    , taskManagerProvider_(std::move(taskManagerProvider))
-    , monitorProvider_(std::move(monitorProvider))
-    , state_(std::move(state))
-    , startSequence_(config.get().maybeValue<uint32_t>("start_sequence"))
-    , finishSequence_(config.get().maybeValue<uint32_t>("finish_sequence"))
+// Database must be populated when this starts
+std::optional<uint32_t>
+ETLService::runETLPipeline(uint32_t startSequence, uint32_t numExtractors)
 {
-    ASSERT(not state_->isWriting, "ETL should never start in writer mode");
+    if (finishSequence_ && startSequence > *finishSequence_)
+        return {};

-    if (startSequence_.has_value())
-        LOG(log_.info()) << "Start sequence: " << *startSequence_;
+    LOG(log_.debug()) << "Wait for cache containing seq " << startSequence - 1
+                      << " current cache last seq =" << backend_->cache().latestLedgerSequence();
+    backend_->cache().waitUntilCacheContainsSeq(startSequence - 1);

-    if (finishSequence_.has_value())
-        LOG(log_.info()) << "Finish sequence: " << *finishSequence_;
+    LOG(log_.debug()) << "Starting etl pipeline";
+    state_.isWriting = true;

-    LOG(log_.info()) << "Starting in " << (state_->isStrictReadonly ? "STRICT READONLY MODE" : "WRITE MODE");
+    auto const rng = backend_->hardFetchLedgerRangeNoThrow();
+    ASSERT(rng.has_value(), "Parent ledger range can't be null");
+    ASSERT(
+        rng->maxSequence >= startSequence - 1,
+        "Got not parent ledger. rnd->maxSequence = {}, startSequence = {}",
+        rng->maxSequence,
+        startSequence
+    );
+
+    auto const begin = std::chrono::system_clock::now();
+    auto extractors = std::vector<std::unique_ptr<ExtractorType>>{};
+    auto pipe = DataPipeType{numExtractors, startSequence};
+
+    for (auto i = 0u; i < numExtractors; ++i) {
+        extractors.push_back(
+            std::make_unique<ExtractorType>(
+                pipe, networkValidatedLedgers_, ledgerFetcher_, startSequence + i, finishSequence_, state_
+            )
+        );
+    }
+
+    auto transformer =
+        TransformerType{pipe, backend_, ledgerLoader_, ledgerPublisher_, amendmentBlockHandler_, startSequence, state_};
+    transformer.waitTillFinished();  // suspend current thread until exit condition is met
+    pipe.cleanup();                  // TODO: this should probably happen automatically using destructor
+
+    // wait for all of the extractors to stop
+    for (auto& t : extractors)
+        t->waitTillFinished();
+
+    auto const end = std::chrono::system_clock::now();
+    auto const lastPublishedSeq = ledgerPublisher_.getLastPublishedSequence();
+    static constexpr auto kNANOSECONDS_PER_SECOND = 1'000'000'000.0;
+    LOG(log_.debug()) << "Extracted and wrote " << lastPublishedSeq.value_or(startSequence) - startSequence << " in "
+                      << ((end - begin).count()) / kNANOSECONDS_PER_SECOND;
+
+    state_.isWriting = false;
+
+    LOG(log_.debug()) << "Stopping etl pipeline";
+    return lastPublishedSeq;
 }

-ETLService::~ETLService()
+// Main loop of ETL.
+// The software begins monitoring the ledgers that are validated by the network.
+// The member networkValidatedLedgers_ keeps track of the sequences of ledgers validated by the network.
+// Whenever a ledger is validated by the network, the software looks for that ledger in the database. Once the ledger is
+// found in the database, the software publishes that ledger to the ledgers stream. If a network validated ledger is not
+// found in the database after a certain amount of time, then the software attempts to take over responsibility of the
+// ETL process, where it writes new ledgers to the database. The software will relinquish control of the ETL process if
+// it detects that another process has taken over ETL.
+void
+ETLService::monitor()
 {
-    stop();
-    LOG(log_.debug()) << "Destroying ETL";
+    auto rng = backend_->hardFetchLedgerRangeNoThrow();
+    if (!rng) {
+        LOG(log_.info()) << "Database is empty. Will download a ledger from the network.";
+        std::optional<ripple::LedgerHeader> ledger;
+
+        try {
+            if (startSequence_) {
+                LOG(log_.info()) << "ledger sequence specified in config. "
+                                 << "Will begin ETL process starting with ledger " << *startSequence_;
+                ledger = ledgerLoader_.loadInitialLedger(*startSequence_);
+            } else {
+                LOG(log_.info()) << "Waiting for next ledger to be validated by network...";
+                std::optional<uint32_t> mostRecentValidated = networkValidatedLedgers_->getMostRecent();
+
+                if (mostRecentValidated) {
+                    LOG(log_.info()) << "Ledger " << *mostRecentValidated << " has been validated. Downloading...";
+                    ledger = ledgerLoader_.loadInitialLedger(*mostRecentValidated);
+                } else {
+                    LOG(log_.info()) << "The wait for the next validated ledger has been aborted. "
+                                        "Exiting monitor loop";
+                    return;
+                }
+            }
+        } catch (std::runtime_error const& e) {
+            LOG(log_.fatal()) << "Failed to load initial ledger: " << e.what();
+            amendmentBlockHandler_.notifyAmendmentBlocked();
+            return;
+        }
+
+        if (ledger) {
+            rng = backend_->hardFetchLedgerRangeNoThrow();
+        } else {
+            LOG(log_.error()) << "Failed to load initial ledger. Exiting monitor loop";
+            return;
+        }
+    } else {
+        if (startSequence_)
+            LOG(log_.warn()) << "start sequence specified but db is already populated";
+
+        LOG(log_.info()) << "Database already populated. Picking up from the tip of history";
+        cacheLoader_.load(rng->maxSequence);
+    }
+
+    ASSERT(rng.has_value(), "Ledger range can't be null");
+    uint32_t nextSequence = rng->maxSequence + 1;
+
+    LOG(log_.debug()) << "Database is populated. Starting monitor loop. sequence = " << nextSequence;
+
+    while (not isStopping()) {
+        nextSequence = publishNextSequence(nextSequence);
+    }
+}
+
+uint32_t
+ETLService::publishNextSequence(uint32_t nextSequence)
+{
+    if (auto rng = backend_->hardFetchLedgerRangeNoThrow(); rng && rng->maxSequence >= nextSequence) {
+        ledgerPublisher_.publish(nextSequence, {});
+        ++nextSequence;
+    } else if (networkValidatedLedgers_->waitUntilValidatedByNetwork(nextSequence, util::kMILLISECONDS_PER_SECOND)) {
+        LOG(log_.info()) << "Ledger with sequence = " << nextSequence << " has been validated by the network. "
+                         << "Attempting to find in database and publish";
+
+        // Attempt to take over responsibility of ETL writer after 10 failed
+        // attempts to publish the ledger. publishLedger() fails if the
+        // ledger that has been validated by the network is not found in the
+        // database after the specified number of attempts. publishLedger()
+        // waits one second between each attempt to read the ledger from the
+        // database
+        constexpr size_t kTIMEOUT_SECONDS = 10;
+        bool const success = ledgerPublisher_.publish(nextSequence, kTIMEOUT_SECONDS);
+
+        if (!success) {
+            LOG(log_.warn()) << "Failed to publish ledger with sequence = " << nextSequence << " . Beginning ETL";
+
+            // returns the most recent sequence published. empty optional if no sequence was published
+            std::optional<uint32_t> lastPublished = runETLPipeline(nextSequence, extractorThreads_);
+            LOG(log_.info()) << "Aborting ETL. Falling back to publishing";
+
+            // if no ledger was published, don't increment nextSequence
+            if (lastPublished)
+                nextSequence = *lastPublished + 1;
+        } else {
+            ++nextSequence;
+        }
+    }
+    return nextSequence;
+}
+
+void
+ETLService::monitorReadOnly()
+{
+    LOG(log_.debug()) << "Starting reporting in strict read only mode";
+
+    auto const latestSequenceOpt = [this]() -> std::optional<uint32_t> {
+        auto rng = backend_->hardFetchLedgerRangeNoThrow();
+
+        if (!rng) {
+            if (auto net = networkValidatedLedgers_->getMostRecent()) {
+                return net;
+            }
+            return std::nullopt;
+        }
+
+        return rng->maxSequence;
+    }();
+
+    if (!latestSequenceOpt.has_value()) {
+        return;
+    }
+
+    uint32_t latestSequence = *latestSequenceOpt;
+
+    cacheLoader_.load(latestSequence);
+    latestSequence++;
+
+    while (not isStopping()) {
+        if (auto rng = backend_->hardFetchLedgerRangeNoThrow(); rng && rng->maxSequence >= latestSequence) {
+            ledgerPublisher_.publish(latestSequence, {});
+            latestSequence = latestSequence + 1;
+        } else {
+            // if we can't, wait until it's validated by the network, or 1 second passes, whichever occurs
+            // first. Even if we don't hear from rippled, if ledgers are being written to the db, we publish
+            // them.
+            networkValidatedLedgers_->waitUntilValidatedByNetwork(latestSequence, util::kMILLISECONDS_PER_SECOND);
+        }
+    }
 }

 void
 ETLService::run()
 {
-    LOG(log_.info()) << "Running ETL...";
+    LOG(log_.info()) << "Starting reporting etl";
+    state_.isStopping = false;

-    mainLoop_.emplace(ctx_.execute([this] {
-        auto const rng = loadInitialLedgerIfNeeded();
-
-        LOG(log_.info()) << "Waiting for next ledger to be validated by network...";
-        std::optional<uint32_t> const mostRecentValidated = ledgers_->getMostRecent();
-
-        if (not mostRecentValidated) {
-            LOG(log_.info()) << "The wait for the next validated ledger has been aborted. "
-                                "Exiting monitor loop";
-            return;
-        }
-
-        if (not rng.has_value()) {
-            LOG(log_.warn()) << "Initial ledger download got cancelled - stopping ETL service";
-            return;
-        }
-
-        auto nextSequence = rng->maxSequence + 1;
-        if (backend_->cache().latestLedgerSequence() != 0) {
-            nextSequence = backend_->cache().latestLedgerSequence();
-        }
-
-        LOG(log_.debug()) << "Database is populated. Starting monitor loop. sequence = " << nextSequence;
-        startMonitor(nextSequence);
-
-        // If we are a writer as the result of loading the initial ledger - start loading
-        if (state_->isWriting)
-            startLoading(nextSequence);
-    }));
+    doWork();
 }

 void
-ETLService::stop()
+ETLService::doWork()
 {
-    LOG(log_.info()) << "Stop called";
+    worker_ = std::thread([this]() {
+        beast::setCurrentThreadName("ETLService worker");

-    if (mainLoop_)
-        mainLoop_->wait();
-    if (taskMan_)
-        taskMan_->stop();
-    if (monitor_)
-        monitor_->stop();
-}
-
-boost::json::object
-ETLService::getInfo() const
-{
-    boost::json::object result;
-
-    result["etl_sources"] = balancer_->toJson();
-    result["is_writer"] = static_cast<int>(state_->isWriting);
-    result["read_only"] = static_cast<int>(state_->isStrictReadonly);
-    auto last = publisher_->getLastPublish();
-    if (last.time_since_epoch().count() != 0)
-        result["last_publish_age_seconds"] = std::to_string(publisher_->lastPublishAgeSeconds());
-    return result;
-}
-
-bool
-ETLService::isAmendmentBlocked() const
-{
-    return state_->isAmendmentBlocked;
-}
-
-bool
-ETLService::isCorruptionDetected() const
-{
-    return state_->isCorruptionDetected;
-}
-
-std::optional<ETLState>
-ETLService::getETLState() const
-{
-    return balancer_->getETLState();
-}
-
-std::uint32_t
-ETLService::lastCloseAgeSeconds() const
-{
-    return publisher_->lastCloseAgeSeconds();
-}
-
-std::optional<data::LedgerRange>
-ETLService::loadInitialLedgerIfNeeded()
-{
-    auto rng = backend_->hardFetchLedgerRangeNoThrow();
-    if (not rng.has_value()) {
-        ASSERT(
-            not state_->isStrictReadonly,
-            "Database is empty but this node is in strict readonly mode. Can't write initial ledger."
-        );
-
-        LOG(log_.info()) << "Database is empty. Will download a ledger from the network.";
-        state_->isWriting = true;  // immediately become writer as the db is empty
-
-        auto const getMostRecent = [this]() {
-            LOG(log_.info()) << "Waiting for next ledger to be validated by network...";
-            return ledgers_->getMostRecent();
-        };
-
-        if (auto const maybeSeq = startSequence_.or_else(getMostRecent); maybeSeq.has_value()) {
-            auto const seq = *maybeSeq;
-            LOG(log_.info()) << "Starting from sequence " << seq
-                             << ". Initial ledger download and extraction can take a while...";
-
-            auto [ledger, timeDiff] = ::util::timed<std::chrono::duration<double>>([this, seq]() {
-                return extractor_->extractLedgerOnly(seq).and_then(
-                    [this, seq](auto&& data) -> std::optional<ripple::LedgerHeader> {
-                        // TODO: loadInitialLedger in balancer should be called fetchEdgeKeys or similar
-                        auto res = balancer_->loadInitialLedger(seq, *initialLoadObserver_);
-                        if (not res.has_value() and res.error() == InitialLedgerLoadError::Cancelled) {
-                            LOG(log_.debug()) << "Initial ledger load got cancelled";
-                            return std::nullopt;
-                        }
-
-                        ASSERT(res.has_value(), "Initial ledger retry logic failed");
-                        data.edgeKeys = std::move(res).value();
-
-                        return loader_->loadInitialLedger(data);
-                    }
-                );
-            });
-
-            if (not ledger.has_value()) {
-                LOG(log_.error()) << "Failed to load initial ledger. Exiting monitor loop";
-                return std::nullopt;
-            }
-
-            LOG(log_.debug()) << "Time to download and store ledger = " << timeDiff;
-            LOG(log_.info()) << "Finished loadInitialLedger. cache size = " << backend_->cache().size();
-
-            return backend_->hardFetchLedgerRangeNoThrow();
+        if (state_.isStrictReadonly) {
+            monitorReadOnly();
+        } else {
+            monitor();
        }
-
-        LOG(log_.info()) << "The wait for the next validated ledger has been aborted. "
-                            "Exiting monitor loop";
-        return std::nullopt;
-    }
-
-    LOG(log_.info()) << "Database already populated. Picking up from the tip of history";
-    if (not backend_->cache().isFull()) {
-        cacheLoader_->load(rng->maxSequence);
-    }
-
-    return rng;
-}
-
-void
-ETLService::startMonitor(uint32_t seq)
-{
-    monitor_ = monitorProvider_->make(ctx_, backend_, ledgers_, seq);
-
-    monitorNewSeqSubscription_ = monitor_->subscribeToNewSequence([this](uint32_t seq) {
-        LOG(log_.info()) << "ETLService (via Monitor) got new seq from db: " << seq;
-
-        if (state_->writeConflict) {
-            LOG(log_.info()) << "Got a write conflict; Giving up writer seat immediately";
-            giveUpWriter();
-        }
-
-        if (not state_->isWriting) {
-            auto const diff = data::synchronousAndRetryOnTimeout([this, seq](auto yield) {
-                return backend_->fetchLedgerDiff(seq, yield);
-            });
-
-            cacheUpdater_->update(seq, diff);
-            backend_->updateRange(seq);
-        }
-
-        publisher_->publish(seq, {});
    });
-
-    monitorDbStalledSubscription_ = monitor_->subscribeToDbStalled([this]() {
-        LOG(log_.warn()) << "ETLService received DbStalled signal from Monitor";
-        if (not state_->isStrictReadonly and not state_->isWriting)
-            attemptTakeoverWriter();
-    });
-
-    monitor_->run();
 }

-void
-ETLService::startLoading(uint32_t seq)
+ETLService::ETLService(
+    util::config::ClioConfigDefinition const& config,
+    boost::asio::io_context& ioc,
+    std::shared_ptr<BackendInterface> backend,
+    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
+    std::shared_ptr<etlng::LoadBalancerInterface> balancer,
+    std::shared_ptr<NetworkValidatedLedgersInterface> ledgers
+)
+    : backend_(backend)
+    , loadBalancer_(balancer)
+    , networkValidatedLedgers_(std::move(ledgers))
+    , cacheLoader_(config, backend, backend->cache())
+    , ledgerFetcher_(backend, balancer)
+    , ledgerLoader_(backend, balancer, ledgerFetcher_, state_)
+    , ledgerPublisher_(ioc, backend, backend->cache(), subscriptions, state_)
+    , amendmentBlockHandler_(ioc, state_)
 {
-    ASSERT(not state_->isStrictReadonly, "This should only happen on writer nodes");
-    taskMan_ = taskManagerProvider_->make(ctx_, *monitor_, seq, finishSequence_);
+    startSequence_ = config.maybeValue<uint32_t>("start_sequence");
+    finishSequence_ = config.maybeValue<uint32_t>("finish_sequence");
+    state_.isStrictReadonly = config.get<bool>("read_only");
+    extractorThreads_ = config.get<uint32_t>("extractor_threads");

-    // FIXME: this legacy name "extractor_threads" is no longer accurate (we have coroutines now)
-    taskMan_->run(config_.get().get<std::size_t>("extractor_threads"));
+    // This should probably be done in the backend factory but we don't have state available until here
+    backend_->setCorruptionDetector(CorruptionDetector{state_, backend->cache()});
 }
-
-void
-ETLService::attemptTakeoverWriter()
-{
-    ASSERT(not state_->isStrictReadonly, "This should only happen on writer nodes");
-    auto rng = backend_->hardFetchLedgerRangeNoThrow();
-    ASSERT(rng.has_value(), "Ledger range can't be null");
-
-    state_->isWriting = true;  // switch to writer
-    LOG(log_.info()) << "Taking over the ETL writer seat";
-    startLoading(rng->maxSequence + 1);
-}
-
-void
-ETLService::giveUpWriter()
-{
-    ASSERT(not state_->isStrictReadonly, "This should only happen on writer nodes");
-    state_->isWriting = false;
-    state_->writeConflict = false;
-    taskMan_ = nullptr;
-}
-
 }  // namespace etl
--- a/src/etl/ETLService.hpp
+++ b/src/etl/ETLService.hpp
@@ -1,7 +1,7 @@
 //------------------------------------------------------------------------------
 /*
    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
+    Copyright (c) 2023, the clio developers.

    Permission to use, copy, modify, and distribute this software for any
    purpose with or without fee is hereby granted, provided that the above
@@ -20,64 +20,57 @@
 #pragma once

 #include "data/BackendInterface.hpp"
-#include "data/Types.hpp"
-#include "etl/CacheLoaderInterface.hpp"
-#include "etl/CacheUpdaterInterface.hpp"
-#include "etl/ETLServiceInterface.hpp"
+#include "etl/CacheLoader.hpp"
 #include "etl/ETLState.hpp"
-#include "etl/ExtractorInterface.hpp"
-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LedgerPublisherInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
-#include "etl/LoaderInterface.hpp"
-#include "etl/MonitorInterface.hpp"
-#include "etl/MonitorProviderInterface.hpp"
 #include "etl/NetworkValidatedLedgersInterface.hpp"
 #include "etl/SystemState.hpp"
-#include "etl/TaskManagerInterface.hpp"
-#include "etl/TaskManagerProviderInterface.hpp"
 #include "etl/impl/AmendmentBlockHandler.hpp"
-#include "etl/impl/CacheUpdater.hpp"
-#include "etl/impl/Extraction.hpp"
+#include "etl/impl/ExtractionDataPipe.hpp"
+#include "etl/impl/Extractor.hpp"
 #include "etl/impl/LedgerFetcher.hpp"
+#include "etl/impl/LedgerLoader.hpp"
 #include "etl/impl/LedgerPublisher.hpp"
-#include "etl/impl/Loading.hpp"
-#include "etl/impl/Registry.hpp"
-#include "etl/impl/Scheduling.hpp"
-#include "etl/impl/TaskManager.hpp"
-#include "etl/impl/ext/Cache.hpp"
-#include "etl/impl/ext/Core.hpp"
-#include "etl/impl/ext/NFT.hpp"
-#include "etl/impl/ext/Successor.hpp"
+#include "etl/impl/Transformer.hpp"
+#include "etlng/ETLServiceInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
+#include "etlng/impl/LedgerPublisher.hpp"
+#include "etlng/impl/TaskManagerProvider.hpp"
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "util/async/AnyExecutionContext.hpp"
-#include "util/async/AnyOperation.hpp"
-#include "util/config/ConfigDefinition.hpp"
 #include "util/log/Logger.hpp"

 #include <boost/asio/io_context.hpp>
 #include <boost/json/object.hpp>
-#include <boost/signals2/connection.hpp>
-#include <fmt/format.h>
-#include <xrpl/basics/Blob.h>
-#include <xrpl/basics/base_uint.h>
-#include <xrpl/basics/strHex.h>
-#include <xrpl/proto/org/xrpl/rpc/v1/get_ledger.pb.h>
-#include <xrpl/proto/org/xrpl/rpc/v1/ledger.pb.h>
-#include <xrpl/protocol/LedgerHeader.h>
-#include <xrpl/protocol/STTx.h>
-#include <xrpl/protocol/TxFormats.h>
-#include <xrpl/protocol/TxMeta.h>
+#include <grpcpp/grpcpp.h>
+#include <org/xrpl/rpc/v1/get_ledger.pb.h>
+#include <xrpl/proto/org/xrpl/rpc/v1/xrp_ledger.grpc.pb.h>

 #include <cstddef>
 #include <cstdint>
-#include <functional>
 #include <memory>
 #include <optional>
 #include <string>
+#include <thread>

+struct AccountTransactionsData;
+struct NFTTransactionsData;
+struct NFTsData;
+
+/**
+ * @brief This namespace contains everything to do with the ETL and ETL sources.
+ */
 namespace etl {

+/**
+ * @brief A tag class to help identify ETLService in templated code.
+ */
+struct ETLServiceTag {
+    virtual ~ETLServiceTag() = default;
+};
+
+template <typename T>
+concept SomeETLService = std::derived_from<T, ETLServiceTag>;
+
 /**
 * @brief This class is responsible for continuously extracting data from a p2p node, and writing that data to the
 * databases.
@@ -91,42 +84,71 @@ namespace etl {
 * the others will fall back to monitoring/publishing. In this sense, this class dynamically transitions from monitoring
 * to writing and from writing to monitoring, based on the activity of other processes running on different machines.
 */
-class ETLService : public ETLServiceInterface {
+class ETLService : public etlng::ETLServiceInterface, ETLServiceTag {
+    // TODO: make these template parameters in ETLService
+    using DataPipeType = etl::impl::ExtractionDataPipe<org::xrpl::rpc::v1::GetLedgerResponse>;
+    using CacheLoaderType = etl::CacheLoader<>;
+    using LedgerFetcherType = etl::impl::LedgerFetcher;
+    using ExtractorType = etl::impl::Extractor<DataPipeType, LedgerFetcherType>;
+    using LedgerLoaderType = etl::impl::LedgerLoader<LedgerFetcherType>;
+    using LedgerPublisherType = etl::impl::LedgerPublisher;
+    using AmendmentBlockHandlerType = etl::impl::AmendmentBlockHandler;
+    using TransformerType =
+        etl::impl::Transformer<DataPipeType, LedgerLoaderType, LedgerPublisherType, AmendmentBlockHandlerType>;
+
    util::Logger log_{"ETL"};

-    util::async::AnyExecutionContext ctx_;
-    std::reference_wrapper<util::config::ClioConfigDefinition const> config_;
    std::shared_ptr<BackendInterface> backend_;
-    std::shared_ptr<LoadBalancerInterface> balancer_;
-    std::shared_ptr<NetworkValidatedLedgersInterface> ledgers_;
-    std::shared_ptr<LedgerPublisherInterface> publisher_;
-    std::shared_ptr<CacheLoaderInterface> cacheLoader_;
-    std::shared_ptr<CacheUpdaterInterface> cacheUpdater_;
-    std::shared_ptr<ExtractorInterface> extractor_;
-    std::shared_ptr<LoaderInterface> loader_;
-    std::shared_ptr<InitialLoadObserverInterface> initialLoadObserver_;
-    std::shared_ptr<TaskManagerProviderInterface> taskManagerProvider_;
-    std::shared_ptr<MonitorProviderInterface> monitorProvider_;
-    std::shared_ptr<SystemState> state_;
+    std::shared_ptr<etlng::LoadBalancerInterface> loadBalancer_;
+    std::shared_ptr<NetworkValidatedLedgersInterface> networkValidatedLedgers_;

+    std::uint32_t extractorThreads_ = 1;
+    std::thread worker_;
+
+    CacheLoaderType cacheLoader_;
+    LedgerFetcherType ledgerFetcher_;
+    LedgerLoaderType ledgerLoader_;
+    LedgerPublisherType ledgerPublisher_;
+    AmendmentBlockHandlerType amendmentBlockHandler_;
+
+    SystemState state_;
+
+    size_t numMarkers_ = 2;
    std::optional<uint32_t> startSequence_;
    std::optional<uint32_t> finishSequence_;

-    std::unique_ptr<MonitorInterface> monitor_;
-    std::unique_ptr<TaskManagerInterface> taskMan_;
-
-    boost::signals2::scoped_connection monitorNewSeqSubscription_;
-    boost::signals2::scoped_connection monitorDbStalledSubscription_;
-
-    std::optional<util::async::AnyOperation<void>> mainLoop_;
-
 public:
+    /**
+     * @brief Create an instance of ETLService.
+     *
+     * @param config The configuration to use
+     * @param ioc io context to run on
+     * @param backend BackendInterface implementation
+     * @param subscriptions Subscription manager
+     * @param balancer Load balancer to use
+     * @param ledgers The network validated ledgers datastructure
+     */
+    ETLService(
+        util::config::ClioConfigDefinition const& config,
+        boost::asio::io_context& ioc,
+        std::shared_ptr<BackendInterface> backend,
+        std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
+        std::shared_ptr<etlng::LoadBalancerInterface> balancer,
+        std::shared_ptr<NetworkValidatedLedgersInterface> ledgers
+    );
+
+    /**
+     * @brief Move constructor is deleted because ETL service shares its fields by reference
+     */
+    ETLService(ETLService&&) = delete;
+
    /**
     * @brief A factory function to spawn new ETLService instances.
     *
     * Creates and runs the ETL service.
     *
     * @param config The configuration to use
+     * @param ioc io context to run on
     * @param ctx Execution context for asynchronous operations
     * @param backend BackendInterface implementation
     * @param subscriptions Subscription manager
@@ -134,89 +156,182 @@ public:
     * @param ledgers The network validated ledgers datastructure
     * @return A shared pointer to a new instance of ETLService
     */
-    static std::shared_ptr<ETLServiceInterface>
+    static std::shared_ptr<etlng::ETLServiceInterface>
    makeETLService(
        util::config::ClioConfigDefinition const& config,
+        boost::asio::io_context& ioc,
        util::async::AnyExecutionContext ctx,
        std::shared_ptr<BackendInterface> backend,
        std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
-        std::shared_ptr<LoadBalancerInterface> balancer,
+        std::shared_ptr<etlng::LoadBalancerInterface> balancer,
        std::shared_ptr<NetworkValidatedLedgersInterface> ledgers
    );

    /**
-     * @brief Create an instance of ETLService.
-     *
-     * @param ctx The execution context for asynchronous operations
-     * @param config The Clio configuration definition
-     * @param backend Interface to the backend database
-     * @param balancer Load balancer for distributing work
-     * @param ledgers Interface for accessing network validated ledgers
-     * @param publisher Interface for publishing ledger data
-     * @param cacheLoader Interface for loading cache data
-     * @param cacheUpdater Interface for updating cache data
-     * @param extractor The extractor to use
-     * @param loader Interface for loading data
-     * @param initialLoadObserver The observer for initial data loading
-     * @param taskManagerProvider The provider of the task manager instance
-     * @param monitorProvider The provider of the monitor instance
-     * @param state System state tracking object
+     * @brief Stops components and joins worker thread.
     */
-    ETLService(
-        util::async::AnyExecutionContext ctx,
-        std::reference_wrapper<util::config::ClioConfigDefinition const> config,
-        std::shared_ptr<data::BackendInterface> backend,
-        std::shared_ptr<LoadBalancerInterface> balancer,
-        std::shared_ptr<NetworkValidatedLedgersInterface> ledgers,
-        std::shared_ptr<LedgerPublisherInterface> publisher,
-        std::shared_ptr<CacheLoaderInterface> cacheLoader,
-        std::shared_ptr<CacheUpdaterInterface> cacheUpdater,
-        std::shared_ptr<ExtractorInterface> extractor,
-        std::shared_ptr<LoaderInterface> loader,
-        std::shared_ptr<InitialLoadObserverInterface> initialLoadObserver,
-        std::shared_ptr<TaskManagerProviderInterface> taskManagerProvider,
-        std::shared_ptr<MonitorProviderInterface> monitorProvider,
-        std::shared_ptr<SystemState> state
-    );
+    ~ETLService() override
+    {
+        if (not state_.isStopping)
+            stop();
+    }

-    ~ETLService() override;
+    /**
+     * @brief Stop the ETL service.
+     * @note This method blocks until the ETL service has stopped.
+     */
+    void
+    stop() override
+    {
+        LOG(log_.info()) << "Stop called";

+        state_.isStopping = true;
+        cacheLoader_.stop();
+
+        if (worker_.joinable())
+            worker_.join();
+
+        LOG(log_.debug()) << "Joined ETLService worker thread";
+    }
+
+    /**
+     * @brief Get time passed since last ledger close, in seconds.
+     *
+     * @return Time passed since last ledger close
+     */
+    std::uint32_t
+    lastCloseAgeSeconds() const override
+    {
+        return ledgerPublisher_.lastCloseAgeSeconds();
+    }
+
+    /**
+     * @brief Check for the amendment blocked state.
+     *
+     * @return true if currently amendment blocked; false otherwise
+     */
+    bool
+    isAmendmentBlocked() const override
+    {
+        return state_.isAmendmentBlocked;
+    }
+
+    /**
+     * @brief Check whether Clio detected DB corruptions.
+     *
+     * @return true if corruption of DB was detected and cache was stopped.
+     */
+    bool
+    isCorruptionDetected() const override
+    {
+        return state_.isCorruptionDetected;
+    }
+
+    /**
+     * @brief Get state of ETL as a JSON object
+     *
+     * @return The state of ETL as a JSON object
+     */
+    boost::json::object
+    getInfo() const override
+    {
+        boost::json::object result;
+
+        result["etl_sources"] = loadBalancer_->toJson();
+        result["is_writer"] = static_cast<int>(state_.isWriting);
+        result["read_only"] = static_cast<int>(state_.isStrictReadonly);
+        auto last = ledgerPublisher_.getLastPublish();
+        if (last.time_since_epoch().count() != 0)
+            result["last_publish_age_seconds"] = std::to_string(ledgerPublisher_.lastPublishAgeSeconds());
+        return result;
+    }
+
+    /**
+     * @brief Get the etl nodes' state
+     * @return The etl nodes' state, nullopt if etl nodes are not connected
+     */
+    std::optional<etl::ETLState>
+    getETLState() const noexcept override
+    {
+        return loadBalancer_->getETLState();
+    }
+
+    /**
+     * @brief Start all components to run ETL service.
+     */
    void
    run() override;

-    void
-    stop() override;
-
-    boost::json::object
-    getInfo() const override;
-
-    bool
-    isAmendmentBlocked() const override;
-
-    bool
-    isCorruptionDetected() const override;
-
-    std::optional<ETLState>
-    getETLState() const override;
-
-    std::uint32_t
-    lastCloseAgeSeconds() const override;
-
 private:
-    std::optional<data::LedgerRange>
-    loadInitialLedgerIfNeeded();
+    /**
+     * @brief Run the ETL pipeline.
+     *
+     * Extracts ledgers and writes them to the database, until a write conflict occurs (or the server shuts down).
+     * @note database must already be populated when this function is called
+     *
+     * @param startSequence the first ledger to extract
+     * @param numExtractors number of extractors to use
+     * @return The last ledger written to the database, if any
+     */
+    std::optional<uint32_t>
+    runETLPipeline(uint32_t startSequence, uint32_t numExtractors);

+    /**
+     * @brief Monitor the network for newly validated ledgers.
+     *
+     * Also monitor the database to see if any process is writing those ledgers.
+     * This function is called when the application starts, and will only return when the application is shutting down.
+     * If the software detects the database is empty, this function will call loadInitialLedger(). If the software
+     * detects ledgers are not being written, this function calls runETLPipeline(). Otherwise, this function publishes
+     * ledgers as they are written to the database.
+     */
    void
-    startMonitor(uint32_t seq);
+    monitor();

-    void
-    startLoading(uint32_t seq);
+    /**
+     * @brief Monitor the network for newly validated ledgers and publish them to the ledgers stream
+     *
+     * @param nextSequence the ledger sequence to publish
+     * @return The next ledger sequence to publish
+     */
+    uint32_t
+    publishNextSequence(uint32_t nextSequence);

+    /**
+     * @brief Monitor the database for newly written ledgers.
+     *
+     * Similar to the monitor(), except this function will never call runETLPipeline() or loadInitialLedger().
+     * This function only publishes ledgers as they are written to the database.
+     */
    void
-    attemptTakeoverWriter();
+    monitorReadOnly();

+    /**
+     * @return true if stopping; false otherwise
+     */
+    bool
+    isStopping() const
+    {
+        return state_.isStopping;
+    }
+
+    /**
+     * @brief Get the number of markers to use during the initial ledger download.
+     *
+     * This is equivalent to the degree of parallelism during the initial ledger download.
+     *
+     * @return The number of markers
+     */
+    std::uint32_t
+    getNumMarkers() const
+    {
+        return numMarkers_;
+    }
+
+    /**
+     * @brief Spawn the worker thread and start monitoring.
+     */
    void
-    giveUpWriter();
+    doWork();
 };
-
 }  // namespace etl
--- a/src/etl/LoadBalancer.cpp
+++ b/src/etl/LoadBalancer.cpp
@@ -21,10 +21,9 @@

 #include "data/BackendInterface.hpp"
 #include "etl/ETLState.hpp"
-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
 #include "etl/NetworkValidatedLedgersInterface.hpp"
 #include "etl/Source.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "rpc/Errors.hpp"
 #include "util/Assert.hpp"
@@ -65,7 +64,7 @@ using util::prometheus::Labels;

 namespace etl {

-std::shared_ptr<LoadBalancerInterface>
+std::shared_ptr<etlng::LoadBalancerInterface>
 LoadBalancer::makeLoadBalancer(
    ClioConfigDefinition const& config,
    boost::asio::io_context& ioc,
@@ -159,6 +158,7 @@ LoadBalancer::LoadBalancer(
        auto source = sourceFactory(
            *it,
            ioc,
+            backend,
            subscriptions,
            validatedLedgers,
            forwardingTimeout,
@@ -212,32 +212,26 @@ LoadBalancer::LoadBalancer(
    }
 }

-InitialLedgerLoadResult
-LoadBalancer::loadInitialLedger(
-    uint32_t sequence,
-    InitialLoadObserverInterface& loadObserver,
-    std::chrono::steady_clock::duration retryAfter
-)
+std::vector<std::string>
+LoadBalancer::loadInitialLedger(uint32_t sequence, std::chrono::steady_clock::duration retryAfter)
 {
-    InitialLedgerLoadResult response;
-
+    std::vector<std::string> response;
    execute(
-        [this, &response, &sequence, &loadObserver](auto& source) {
-            auto res = source->loadInitialLedger(sequence, downloadRanges_, loadObserver);
+        [this, &response, &sequence](auto& source) {
+            auto [data, res] = source->loadInitialLedger(sequence, downloadRanges_);

-            if (not res.has_value() and res.error() == InitialLedgerLoadError::Errored) {
+            if (!res) {
                LOG(log_.error()) << "Failed to download initial ledger."
                                  << " Sequence = " << sequence << " source = " << source->toString();
-                return false;  // should retry on error
+            } else {
+                response = std::move(data);
            }

-            response = std::move(res);  // cancelled or data received
-            return true;
+            return res;
        },
        sequence,
        retryAfter
    );
-
    return response;
 }

--- a/src/etl/LoadBalancer.hpp
+++ b/src/etl/LoadBalancer.hpp
@@ -21,12 +21,13 @@

 #include "data/BackendInterface.hpp"
 #include "etl/ETLState.hpp"
-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
 #include "etl/NetworkValidatedLedgersInterface.hpp"
 #include "etl/Source.hpp"
+#include "etlng/InitialLoadObserverInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "rpc/Errors.hpp"
+#include "util/Assert.hpp"
 #include "util/Mutex.hpp"
 #include "util/Random.hpp"
 #include "util/ResponseExpirationCache.hpp"
@@ -53,6 +54,7 @@
 #include <optional>
 #include <string>
 #include <string_view>
+#include <utility>
 #include <vector>

 namespace etl {
@@ -74,7 +76,7 @@ concept SomeLoadBalancer = std::derived_from<T, LoadBalancerTag>;
 * which ledgers have been validated by the network, and the range of ledgers each etl source has). This class also
 * allows requests for ledger data to be load balanced across all possible ETL sources.
 */
-class LoadBalancer : public LoadBalancerInterface, LoadBalancerTag {
+class LoadBalancer : public etlng::LoadBalancerInterface, LoadBalancerTag {
 public:
    using RawLedgerObjectType = org::xrpl::rpc::v1::RawLedgerObject;
    using GetLedgerResponseType = org::xrpl::rpc::v1::GetLedgerResponse;
@@ -147,7 +149,7 @@ public:
     * @param backend BackendInterface implementation
     * @param subscriptions Subscription manager
     * @param randomGenerator A random generator to use for selecting sources
-     * @param validatedLedgers The network validated ledgers datastructure
+     * @param validatedLedgers The network validated ledgers data structure
     * @param sourceFactory A factory function to create a source
     * @return A shared pointer to a new instance of LoadBalancer
     */
@@ -162,6 +164,20 @@ public:
        SourceFactory sourceFactory = makeSource
    );

+    /**
+     * @brief Load the initial ledger, writing data to the queue.
+     * @note This function will retry indefinitely until the ledger is downloaded.
+     *
+     * @param sequence Sequence of ledger to download
+     * @param retryAfter Time to wait between retries (2 seconds by default)
+     * @return A std::vector<std::string> The ledger data
+     */
+    std::vector<std::string>
+    loadInitialLedger(
+        uint32_t sequence,
+        std::chrono::steady_clock::duration retryAfter = std::chrono::seconds{2}
+    ) override;
+
    /**
     * @brief Load the initial ledger, writing data to the queue.
     * @note This function will retry indefinitely until the ledger is downloaded or the download is cancelled.
@@ -171,12 +187,16 @@ public:
     * @param retryAfter Time to wait between retries (2 seconds by default)
     * @return A std::expected with ledger edge keys on success, or InitialLedgerLoadError on failure
     */
-    InitialLedgerLoadResult
+    etlng::InitialLedgerLoadResult
    loadInitialLedger(
-        uint32_t sequence,
-        InitialLoadObserverInterface& observer,
-        std::chrono::steady_clock::duration retryAfter
-    ) override;
+        [[maybe_unused]] uint32_t sequence,
+        [[maybe_unused]] etlng::InitialLoadObserverInterface& observer,
+        [[maybe_unused]] std::chrono::steady_clock::duration retryAfter
+    ) override
+    {
+        ASSERT(false, "Not available for old ETL");
+        std::unreachable();
+    }

    /**
     * @brief Fetch data for a specific ledger.
--- a/src/etl/README.md
+++ b/src/etl/README.md
@@ -6,7 +6,7 @@ A single Clio node has one or more ETL sources specified in the config file. Cli

 Upon receiving a message on the stream, Clio fetches the data associated with the newly validated ledger from one of the ETL sources. The fetch is performed via a gRPC request called `GetLedger`. This request returns the ledger header, transactions and metadata blobs, and every ledger object added/modified/deleted as part of this ledger. The ETL subsystem then writes all of this data to the databases, and moves on to the next ledger.

-If the database is not empty, clio will first come up in a "soft" read-only mode. In read-only mode, the server does not perform ETL and simply publishes new ledgers as they are written to the database. If the database is not updated within a certain time period (currently hard coded at 10 seconds), clio will begin the ETL process and start writing to the database. The database will report an error when trying to write a record with a key that already exists. ETL uses this error to determine that another process is writing to the database, and subsequently falls back to a soft read-only mode. clio can also operate in strict read-only mode, in which case they will never write to the database.
+If the database is not empty, clio will first come up in a "soft" read-only mode. In read-only mode, the server does not perform ETL and simply publishes new ledgers as they are written to the database. If the database is not updated within a certain time period (currently hard coded at 20 seconds), clio will begin the ETL process and start writing to the database. The database will report an error when trying to write a record with a key that already exists. ETL uses this error to determine that another process is writing to the database, and subsequently falls back to a soft read-only mode. clio can also operate in strict read-only mode, in which case they will never write to the database.

 ## Ledger cache

--- a/src/etl/Source.cpp
+++ b/src/etl/Source.cpp
@@ -19,6 +19,7 @@

 #include "etl/Source.hpp"

+#include "data/BackendInterface.hpp"
 #include "etl/NetworkValidatedLedgersInterface.hpp"
 #include "etl/impl/ForwardingSource.hpp"
 #include "etl/impl/GrpcSource.hpp"
@@ -40,6 +41,7 @@ SourcePtr
 makeSource(
    util::config::ObjectView const& config,
    boost::asio::io_context& ioc,
+    std::shared_ptr<BackendInterface> backend,
    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
    std::shared_ptr<NetworkValidatedLedgersInterface> validatedLedgers,
    std::chrono::steady_clock::duration forwardingTimeout,
@@ -53,7 +55,7 @@ makeSource(
    auto const grpcPort = config.get<std::string>("grpc_port");

    impl::ForwardingSource forwardingSource{ip, wsPort, forwardingTimeout};
-    impl::GrpcSource grpcSource{ip, grpcPort};
+    impl::GrpcSource grpcSource{ip, grpcPort, std::move(backend)};
    auto subscriptionSource = std::make_unique<impl::SubscriptionSource>(
        ioc,
        ip,
--- a/src/etl/Source.hpp
+++ b/src/etl/Source.hpp
@@ -19,8 +19,7 @@

 #pragma once

-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
+#include "data/BackendInterface.hpp"
 #include "etl/NetworkValidatedLedgersInterface.hpp"
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "rpc/Errors.hpp"
@@ -48,6 +47,7 @@ namespace etl {

 /**
 * @brief Provides an implementation of a ETL source
+ *
 */
 class SourceBase {
 public:
@@ -77,7 +77,7 @@ public:
     *
     * @return true if source is connected; false otherwise
     */
-    [[nodiscard]] virtual bool
+    virtual bool
    isConnected() const = 0;

    /**
@@ -93,11 +93,11 @@ public:
     *
     * @return JSON representation of the source
     */
-    [[nodiscard]] virtual boost::json::object
+    virtual boost::json::object
    toJson() const = 0;

    /** @return String representation of the source (for debug) */
-    [[nodiscard]] virtual std::string
+    virtual std::string
    toString() const = 0;

    /**
@@ -106,7 +106,7 @@ public:
     * @param sequence The ledger sequence to check
     * @return true if ledger is in the range of this source; false otherwise
     */
-    [[nodiscard]] virtual bool
+    virtual bool
    hasLedger(uint32_t sequence) const = 0;

    /**
@@ -120,7 +120,7 @@ public:
     * @param getObjectNeighbors Whether to request object neighbors; defaults to false
     * @return A std::pair of the response status and the response itself
     */
-    [[nodiscard]] virtual std::pair<grpc::Status, org::xrpl::rpc::v1::GetLedgerResponse>
+    virtual std::pair<grpc::Status, org::xrpl::rpc::v1::GetLedgerResponse>
    fetchLedger(uint32_t sequence, bool getObjects = true, bool getObjectNeighbors = false) = 0;

    /**
@@ -128,11 +128,10 @@ public:
     *
     * @param sequence Sequence of the ledger to download
     * @param numMarkers Number of markers to generate for async calls
-     * @param loader InitialLoadObserverInterface implementation
     * @return A std::pair of the data and a bool indicating whether the download was successful
     */
-    virtual InitialLedgerLoadResult
-    loadInitialLedger(uint32_t sequence, std::uint32_t numMarkers, InitialLoadObserverInterface& loader) = 0;
+    virtual std::pair<std::vector<std::string>, bool>
+    loadInitialLedger(uint32_t sequence, std::uint32_t numMarkers) = 0;

    /**
     * @brief Forward a request to rippled.
@@ -143,7 +142,7 @@ public:
     * @param yield The coroutine context
     * @return Response on success or error on failure
     */
-    [[nodiscard]] virtual std::expected<boost::json::object, rpc::ClioError>
+    virtual std::expected<boost::json::object, rpc::ClioError>
    forwardToRippled(
        boost::json::object const& request,
        std::optional<std::string> const& forwardToRippledClientIp,
@@ -157,6 +156,7 @@ using SourcePtr = std::unique_ptr<SourceBase>;
 using SourceFactory = std::function<SourcePtr(
    util::config::ObjectView const& config,
    boost::asio::io_context& ioc,
+    std::shared_ptr<BackendInterface> backend,
    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
    std::shared_ptr<NetworkValidatedLedgersInterface> validatedLedgers,
    std::chrono::steady_clock::duration forwardingTimeout,
@@ -170,6 +170,7 @@ using SourceFactory = std::function<SourcePtr(
 *
 * @param config The configuration to use
 * @param ioc The io_context to run on
+ * @param backend BackendInterface implementation
 * @param subscriptions Subscription manager
 * @param validatedLedgers The network validated ledgers data structure
 * @param forwardingTimeout The timeout for forwarding to rippled
@@ -179,10 +180,11 @@ using SourceFactory = std::function<SourcePtr(
 * as forwarding.
 * @return The created source
 */
-[[nodiscard]] SourcePtr
+SourcePtr
 makeSource(
    util::config::ObjectView const& config,
    boost::asio::io_context& ioc,
+    std::shared_ptr<BackendInterface> backend,
    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
    std::shared_ptr<NetworkValidatedLedgersInterface> validatedLedgers,
    std::chrono::steady_clock::duration forwardingTimeout,
--- a/src/etl/impl/AmendmentBlockHandler.cpp
+++ b/src/etl/impl/AmendmentBlockHandler.cpp
@@ -20,12 +20,12 @@
 #include "etl/impl/AmendmentBlockHandler.hpp"

 #include "etl/SystemState.hpp"
-#include "util/async/AnyExecutionContext.hpp"
 #include "util/log/Logger.hpp"

+#include <boost/asio/io_context.hpp>
+
 #include <chrono>
 #include <functional>
-#include <optional>
 #include <utility>

 namespace etl::impl {
@@ -37,35 +37,20 @@ AmendmentBlockHandler::ActionType const AmendmentBlockHandler::kDEFAULT_AMENDMEN
 };

 AmendmentBlockHandler::AmendmentBlockHandler(
-    util::async::AnyExecutionContext ctx,
+    boost::asio::io_context& ioc,
    SystemState& state,
    std::chrono::steady_clock::duration interval,
    ActionType action
 )
-    : state_{std::ref(state)}, interval_{interval}, ctx_{std::move(ctx)}, action_{std::move(action)}
+    : state_{std::ref(state)}, repeat_{ioc}, interval_{interval}, action_{std::move(action)}
 {
 }

-AmendmentBlockHandler::~AmendmentBlockHandler()
-{
-    stop();
-}
-
 void
 AmendmentBlockHandler::notifyAmendmentBlocked()
 {
    state_.get().isAmendmentBlocked = true;
-    if (not operation_.has_value())
-        operation_.emplace(ctx_.executeRepeatedly(interval_, action_));
-}
-
-void
-AmendmentBlockHandler::stop()
-{
-    if (operation_.has_value()) {
-        operation_->abort();
-        operation_.reset();
-    }
+    repeat_.start(interval_, action_);
 }

 }  // namespace etl::impl
--- a/src/etl/impl/AmendmentBlockHandler.hpp
+++ b/src/etl/impl/AmendmentBlockHandler.hpp
@@ -1,7 +1,7 @@
 //------------------------------------------------------------------------------
 /*
    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2024, the clio developers.
+    Copyright (c) 2023, the clio developers.

    Permission to use, copy, modify, and distribute this software for any
    purpose with or without fee is hereby granted, provided that the above
@@ -19,10 +19,8 @@

 #pragma once

-#include "etl/AmendmentBlockHandlerInterface.hpp"
 #include "etl/SystemState.hpp"
-#include "util/async/AnyExecutionContext.hpp"
-#include "util/async/AnyOperation.hpp"
+#include "util/Repeat.hpp"

 #include <boost/asio/io_context.hpp>
 #include <boost/asio/post.hpp>
@@ -30,19 +28,17 @@

 #include <chrono>
 #include <functional>
-#include <optional>

 namespace etl::impl {

-class AmendmentBlockHandler : public AmendmentBlockHandlerInterface {
+class AmendmentBlockHandler {
 public:
    using ActionType = std::function<void()>;

 private:
    std::reference_wrapper<SystemState> state_;
+    util::Repeat repeat_;
    std::chrono::steady_clock::duration interval_;
-    util::async::AnyExecutionContext ctx_;
-    std::optional<util::async::AnyOperation<void>> operation_;

    ActionType action_;

@@ -50,19 +46,14 @@ public:
    static ActionType const kDEFAULT_AMENDMENT_BLOCK_ACTION;

    AmendmentBlockHandler(
-        util::async::AnyExecutionContext ctx,
+        boost::asio::io_context& ioc,
        SystemState& state,
        std::chrono::steady_clock::duration interval = std::chrono::seconds{1},
        ActionType action = kDEFAULT_AMENDMENT_BLOCK_ACTION
    );

-    ~AmendmentBlockHandler() override;
-
    void
-    stop() override;
-
-    void
-    notifyAmendmentBlocked() override;
+    notifyAmendmentBlocked();
 };

 }  // namespace etl::impl
--- a/src/etl/impl/AsyncData.hpp
+++ b/src/etl/impl/AsyncData.hpp
@@ -0,0 +1,221 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "data/BackendInterface.hpp"
+#include "data/Types.hpp"
+#include "etl/ETLHelpers.hpp"
+#include "etl/MPTHelpers.hpp"
+#include "etl/NFTHelpers.hpp"
+#include "util/Assert.hpp"
+#include "util/log/Logger.hpp"
+
+#include <grpcpp/client_context.h>
+#include <grpcpp/grpcpp.h>
+#include <grpcpp/support/status.h>
+#include <org/xrpl/rpc/v1/get_ledger_data.pb.h>
+#include <xrpl/basics/base_uint.h>
+#include <xrpl/basics/strHex.h>
+#include <xrpl/proto/org/xrpl/rpc/v1/xrp_ledger.grpc.pb.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <optional>
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace etl::impl {
+
+class AsyncCallData {
+    util::Logger log_{"ETL"};
+
+    std::unique_ptr<org::xrpl::rpc::v1::GetLedgerDataResponse> cur_;
+    std::unique_ptr<org::xrpl::rpc::v1::GetLedgerDataResponse> next_;
+
+    org::xrpl::rpc::v1::GetLedgerDataRequest request_;
+    std::unique_ptr<grpc::ClientContext> context_;
+
+    grpc::Status status_;
+    unsigned char nextPrefix_;
+
+    std::string lastKey_;
+
+public:
+    AsyncCallData(uint32_t seq, ripple::uint256 const& marker, std::optional<ripple::uint256> const& nextMarker)
+    {
+        request_.mutable_ledger()->set_sequence(seq);
+        if (marker.isNonZero()) {
+            request_.set_marker(marker.data(), ripple::uint256::size());
+        }
+        request_.set_user("ETL");
+        nextPrefix_ = 0x00;
+        if (nextMarker)
+            nextPrefix_ = nextMarker->data()[0];
+
+        unsigned char const prefix = marker.data()[0];
+
+        LOG(log_.debug()) << "Setting up AsyncCallData. marker = " << ripple::strHex(marker)
+                          << " . prefix = " << ripple::strHex(std::string(1, prefix))
+                          << " . nextPrefix_ = " << ripple::strHex(std::string(1, nextPrefix_));
+
+        ASSERT(
+            nextPrefix_ > prefix || nextPrefix_ == 0x00,
+            "Next prefix must be greater than current prefix. Got: nextPrefix_ = {}, prefix = {}",
+            nextPrefix_,
+            prefix
+        );
+
+        cur_ = std::make_unique<org::xrpl::rpc::v1::GetLedgerDataResponse>();
+        next_ = std::make_unique<org::xrpl::rpc::v1::GetLedgerDataResponse>();
+        context_ = std::make_unique<grpc::ClientContext>();
+    }
+
+    enum class CallStatus { MORE, DONE, ERRORED };
+
+    CallStatus
+    process(
+        std::unique_ptr<org::xrpl::rpc::v1::XRPLedgerAPIService::Stub>& stub,
+        grpc::CompletionQueue& cq,
+        BackendInterface& backend,
+        bool abort,
+        bool cacheOnly = false
+    )
+    {
+        LOG(log_.trace()) << "Processing response. "
+                          << "Marker prefix = " << getMarkerPrefix();
+        if (abort) {
+            LOG(log_.error()) << "AsyncCallData aborted";
+            return CallStatus::ERRORED;
+        }
+        if (!status_.ok()) {
+            LOG(log_.error()) << "AsyncCallData status_ not ok: code = " << status_.error_code()
+                              << " message = " << status_.error_message();
+            return CallStatus::ERRORED;
+        }
+        if (!next_->is_unlimited()) {
+            LOG(log_.warn()) << "AsyncCallData is_unlimited is false. "
+                             << "Make sure secure_gateway is set correctly at the ETL source";
+        }
+
+        std::swap(cur_, next_);
+
+        bool more = true;
+
+        // if no marker returned, we are done
+        if (cur_->marker().empty())
+            more = false;
+
+        // if returned marker is greater than our end, we are done
+        unsigned char const prefix = cur_->marker()[0];
+        if (nextPrefix_ != 0x00 && prefix >= nextPrefix_)
+            more = false;
+
+        // if we are not done, make the next async call
+        if (more) {
+            request_.set_marker(cur_->marker());
+            call(stub, cq);
+        }
+
+        auto const numObjects = cur_->ledger_objects().objects_size();
+        LOG(log_.debug()) << "Writing " << numObjects << " objects";
+
+        std::vector<data::LedgerObject> cacheUpdates;
+        cacheUpdates.reserve(numObjects);
+
+        for (int i = 0; i < numObjects; ++i) {
+            auto& obj = *(cur_->mutable_ledger_objects()->mutable_objects(i));
+            if (!more && nextPrefix_ != 0x00) {
+                if (static_cast<unsigned char>(obj.key()[0]) >= nextPrefix_)
+                    continue;
+            }
+            cacheUpdates.push_back(
+                {*ripple::uint256::fromVoidChecked(obj.key()), {obj.data().begin(), obj.data().end()}}
+            );
+            if (!cacheOnly) {
+                if (!lastKey_.empty())
+                    backend.writeSuccessor(std::move(lastKey_), request_.ledger().sequence(), std::string{obj.key()});
+                lastKey_ = obj.key();
+                backend.writeNFTs(getNFTDataFromObj(request_.ledger().sequence(), obj.key(), obj.data()));
+
+                auto const maybeMPTHolder = getMPTHolderFromObj(obj.key(), obj.data());
+                if (maybeMPTHolder)
+                    backend.writeMPTHolders({*maybeMPTHolder});
+
+                backend.writeLedgerObject(
+                    std::move(*obj.mutable_key()), request_.ledger().sequence(), std::move(*obj.mutable_data())
+                );
+            }
+        }
+        backend.cache().update(cacheUpdates, request_.ledger().sequence(), cacheOnly);
+        LOG(log_.debug()) << "Wrote " << numObjects << " objects. Got more: " << (more ? "YES" : "NO");
+
+        return more ? CallStatus::MORE : CallStatus::DONE;
+    }
+
+    void
+    call(std::unique_ptr<org::xrpl::rpc::v1::XRPLedgerAPIService::Stub>& stub, grpc::CompletionQueue& cq)
+    {
+        context_ = std::make_unique<grpc::ClientContext>();
+
+        std::unique_ptr<grpc::ClientAsyncResponseReader<org::xrpl::rpc::v1::GetLedgerDataResponse>> rpc(
+            stub->PrepareAsyncGetLedgerData(context_.get(), request_, &cq)
+        );
+
+        rpc->StartCall();
+
+        rpc->Finish(next_.get(), &status_, this);
+    }
+
+    std::string
+    getMarkerPrefix()
+    {
+        if (next_->marker().empty()) {
+            return "";
+        }
+        return ripple::strHex(std::string{next_->marker().data()[0]});
+    }
+
+    std::string
+    getLastKey()
+    {
+        return lastKey_;
+    }
+};
+
+inline std::vector<AsyncCallData>
+makeAsyncCallData(uint32_t const sequence, uint32_t const numMarkers)
+{
+    auto const markers = getMarkers(numMarkers);
+
+    std::vector<AsyncCallData> result;
+    result.reserve(markers.size());
+
+    for (size_t i = 0; i + 1 < markers.size(); ++i) {
+        result.emplace_back(sequence, markers[i], markers[i + 1]);
+    }
+    if (not markers.empty()) {
+        result.emplace_back(sequence, markers.back(), std::nullopt);
+    }
+    return result;
+}
+
+}  // namespace etl::impl
--- a/src/etl/impl/CacheLoader.hpp
+++ b/src/etl/impl/CacheLoader.hpp
@@ -53,7 +53,7 @@ class CacheLoaderImpl {
    std::shared_ptr<BackendInterface> backend_;
    std::reference_wrapper<CacheType> cache_;

-    ThreadSafeQueue<CursorPair> queue_;
+    etl::ThreadSafeQueue<CursorPair> queue_;
    std::atomic_int16_t remaining_;

    std::chrono::steady_clock::time_point startTime_ = std::chrono::steady_clock::now();
--- a/src/etl/impl/ExtractionDataPipe.hpp
+++ b/src/etl/impl/ExtractionDataPipe.hpp
@@ -0,0 +1,136 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "etl/ETLHelpers.hpp"
+#include "util/log/Logger.hpp"
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <optional>
+#include <vector>
+
+namespace etl::impl {
+
+/**
+ * @brief A collection of thread safe async queues used by Extractor and Transformer to communicate
+ */
+template <typename RawDataType>
+class ExtractionDataPipe {
+public:
+    using DataType = std::optional<RawDataType>;
+    using QueueType = ThreadSafeQueue<DataType>;  // TODO: probably should use boost::lockfree::queue instead?
+
+    static constexpr auto kTOTAL_MAX_IN_QUEUE = 1000u;
+
+private:
+    util::Logger log_{"ETL"};
+
+    uint32_t stride_;
+    uint32_t startSequence_;
+
+    std::vector<std::shared_ptr<QueueType>> queues_;
+
+public:
+    /**
+     * @brief Create a new instance of the extraction data pipe
+     *
+     * @param stride
+     * @param startSequence
+     */
+    ExtractionDataPipe(uint32_t stride, uint32_t startSequence) : stride_{stride}, startSequence_{startSequence}
+    {
+        auto const maxQueueSize = kTOTAL_MAX_IN_QUEUE / stride;
+        for (size_t i = 0; i < stride_; ++i)
+            queues_.push_back(std::make_unique<QueueType>(maxQueueSize));
+    }
+
+    /**
+     * @brief Push new data package for the specified sequence.
+     *
+     * Note: Potentially blocks until the underlying queue can accommodate another entry.
+     *
+     * @param sequence The sequence for which to enqueue the data package
+     * @param data The data to store
+     */
+    void
+    push(uint32_t sequence, DataType&& data)
+    {
+        getQueue(sequence)->push(std::move(data));
+    }
+
+    /**
+     * @brief Get data package for the given sequence
+     *
+     * Note: Potentially blocks until data is available.
+     *
+     * @param sequence The sequence for which data is required
+     * @return The data wrapped in an optional; nullopt means that there is no more data to expect
+     */
+    DataType
+    popNext(uint32_t sequence)
+    {
+        return getQueue(sequence)->pop();
+    }
+
+    /**
+     * @return Get the stride
+     */
+    uint32_t
+    getStride() const
+    {
+        return stride_;
+    }
+
+    /**
+     * @brief Hint the Transformer that the queue is done sending data
+     * @param sequence The sequence for which the extractor queue is to be hinted
+     */
+    void
+    finish(uint32_t sequence)
+    {
+        // empty optional hints the Transformer to shut down
+        push(sequence, std::nullopt);
+    }
+
+    /**
+     * @brief Unblocks internal queues
+     *
+     * Note: For now this must be called by the ETL when Transformer exits.
+     */
+    void
+    cleanup()
+    {
+        // TODO: this should not have to be called by hand. it should be done via RAII
+        for (auto i = 0u; i < stride_; ++i)
+            getQueue(i)->tryPop();  // pop from each queue that might be blocked on a push
+    }
+
+private:
+    std::shared_ptr<QueueType>
+    getQueue(uint32_t sequence)
+    {
+        LOG(log_.debug()) << "Grabbing extraction queue for " << sequence << "; start was " << startSequence_;
+        return queues_[(sequence - startSequence_) % stride_];
+    }
+};
+
+}  // namespace etl::impl
--- a/src/etl/impl/Extractor.hpp
+++ b/src/etl/impl/Extractor.hpp
@@ -0,0 +1,147 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "etl/NetworkValidatedLedgersInterface.hpp"
+#include "etl/SystemState.hpp"
+#include "util/Assert.hpp"
+#include "util/Profiler.hpp"
+#include "util/log/Logger.hpp"
+
+#include <xrpl/beast/core/CurrentThreadName.h>
+
+#include <chrono>
+#include <cstdint>
+#include <functional>
+#include <memory>
+#include <optional>
+#include <thread>
+#include <utility>
+
+namespace etl::impl {
+
+/**
+ * @brief Extractor thread that is fetching GRPC data and enqueue it on the DataPipeType
+ */
+template <typename DataPipeType, typename LedgerFetcherType>
+class Extractor {
+    util::Logger log_{"ETL"};
+
+    std::reference_wrapper<DataPipeType> pipe_;
+    std::shared_ptr<NetworkValidatedLedgersInterface> networkValidatedLedgers_;
+    std::reference_wrapper<LedgerFetcherType> ledgerFetcher_;
+    uint32_t startSequence_;
+    std::optional<uint32_t> finishSequence_;
+    std::reference_wrapper<SystemState const> state_;  // shared state for ETL
+
+    std::thread thread_;
+
+public:
+    Extractor(
+        DataPipeType& pipe,
+        std::shared_ptr<NetworkValidatedLedgersInterface> networkValidatedLedgers,
+        LedgerFetcherType& ledgerFetcher,
+        uint32_t startSequence,
+        std::optional<uint32_t> finishSequence,
+        SystemState const& state
+    )
+        : pipe_(std::ref(pipe))
+        , networkValidatedLedgers_{std::move(networkValidatedLedgers)}
+        , ledgerFetcher_{std::ref(ledgerFetcher)}
+        , startSequence_{startSequence}
+        , finishSequence_{finishSequence}
+        , state_{std::cref(state)}
+    {
+        thread_ = std::thread([this]() { process(); });
+    }
+
+    ~Extractor()
+    {
+        if (thread_.joinable())
+            thread_.join();
+    }
+
+    void
+    waitTillFinished()
+    {
+        ASSERT(thread_.joinable(), "Extractor thread must be joinable");
+        thread_.join();
+    }
+
+private:
+    void
+    process()
+    {
+        beast::setCurrentThreadName("ETLService extract");
+
+        double totalTime = 0.0;
+        auto currentSequence = startSequence_;
+
+        while (!shouldFinish(currentSequence) &&
+               networkValidatedLedgers_->waitUntilValidatedByNetwork(currentSequence)) {
+            auto [fetchResponse, time] = ::util::timed<std::chrono::duration<double>>([this, currentSequence]() {
+                return ledgerFetcher_.get().fetchDataAndDiff(currentSequence);
+            });
+            totalTime += time;
+
+            // if the fetch is unsuccessful, stop. fetchLedger only returns false if the server is shutting down, or
+            // if the ledger was found in the database (which means another process already wrote the ledger that
+            // this process was trying to extract; this is a form of a write conflict). Otherwise, fetchDataAndDiff
+            // will keep trying to fetch the specified ledger until successful.
+            if (!fetchResponse)
+                break;
+
+            // TODO: extract this part into a strategy perhaps
+            auto const tps = fetchResponse->transactions_list().transactions_size() / time;
+            LOG(log_.info()) << "Extract phase time = " << time << "; Extract phase tps = " << tps
+                             << "; Avg extract time = " << totalTime / (currentSequence - startSequence_ + 1)
+                             << "; seq = " << currentSequence;
+
+            pipe_.get().push(currentSequence, std::move(fetchResponse));
+            currentSequence += pipe_.get().getStride();
+        }
+
+        pipe_.get().finish(startSequence_);
+    }
+
+    [[nodiscard]] bool
+    isStopping() const
+    {
+        return state_.get().isStopping;
+    }
+
+    [[nodiscard]] bool
+    hasWriteConflict() const
+    {
+        return state_.get().writeConflict;
+    }
+
+    [[nodiscard]] bool
+    shouldFinish(uint32_t seq) const
+    {
+        // Stopping conditions:
+        // - if there is a write conflict in the load thread, the ETL mechanism should stop.
+        // - if the entire server is shutting down - this can be detected in a variety of ways.
+        // - when the given sequence is past the finishSequence in case one is specified
+        return hasWriteConflict() || isStopping() || (finishSequence_ && seq > *finishSequence_);
+    }
+};
+
+}  // namespace etl::impl
--- a/src/etl/impl/GrpcSource.cpp
+++ b/src/etl/impl/GrpcSource.cpp
@@ -19,14 +19,13 @@

 #include "etl/impl/GrpcSource.hpp"

-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
-#include "etl/impl/AsyncGrpcCall.hpp"
+#include "data/BackendInterface.hpp"
+#include "etl/impl/AsyncData.hpp"
 #include "util/Assert.hpp"
 #include "util/log/Logger.hpp"
-#include "web/Resolver.hpp"

-#include <boost/asio/spawn.hpp>
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/ip/tcp.hpp>
 #include <fmt/format.h>
 #include <grpc/grpc.h>
 #include <grpcpp/client_context.h>
@@ -36,41 +35,33 @@
 #include <org/xrpl/rpc/v1/get_ledger.pb.h>
 #include <org/xrpl/rpc/v1/xrp_ledger.grpc.pb.h>

-#include <atomic>
 #include <chrono>
 #include <cstddef>
 #include <cstdint>
 #include <exception>
-#include <expected>
 #include <memory>
+#include <sstream>
 #include <stdexcept>
 #include <string>
 #include <utility>
 #include <vector>

-namespace {
-
-std::string
-resolve(std::string const& ip, std::string const& port)
-{
-    web::Resolver resolver;
-
-    if (auto const results = resolver.resolve(ip, port); not results.empty())
-        return results.at(0);
-
-    throw std::runtime_error("Failed to resolve " + ip + ":" + port);
-}
-
-}  // namespace
-
 namespace etl::impl {

-GrpcSource::GrpcSource(std::string const& ip, std::string const& grpcPort, std::chrono::system_clock::duration deadline)
-    : log_(fmt::format("ETL_Grpc[{}:{}]", ip, grpcPort))
-    , initialLoadShouldStop_(std::make_unique<std::atomic_bool>(false))
-    , deadline_{deadline}
+GrpcSource::GrpcSource(std::string const& ip, std::string const& grpcPort, std::shared_ptr<BackendInterface> backend)
+    : log_(fmt::format("GrpcSource[{}:{}]", ip, grpcPort)), backend_(std::move(backend))
 {
    try {
+        boost::asio::io_context ctx;
+        boost::asio::ip::tcp::resolver resolver{ctx};
+
+        auto const resolverResult = resolver.resolve(ip, grpcPort);
+        if (resolverResult.empty())
+            throw std::runtime_error("Failed to resolve " + ip + ":" + grpcPort);
+
+        std::stringstream ss;
+        ss << resolverResult.begin()->endpoint();
+
        grpc::ChannelArguments chArgs;
        chArgs.SetMaxReceiveMessageSize(-1);
        chArgs.SetInt(GRPC_ARG_KEEPALIVE_TIME_MS, kKEEPALIVE_PING_INTERVAL_MS);
@@ -79,7 +70,7 @@ GrpcSource::GrpcSource(std::string const& ip, std::string const& grpcPort, std::
        chArgs.SetInt(GRPC_ARG_HTTP2_MAX_PINGS_WITHOUT_DATA, kMAX_PINGS_WITHOUT_DATA);

        stub_ = org::xrpl::rpc::v1::XRPLedgerAPIService::NewStub(
-            grpc::CreateCustomChannel(resolve(ip, grpcPort), grpc::InsecureChannelCredentials(), chArgs)
+            grpc::CreateCustomChannel(ss.str(), grpc::InsecureChannelCredentials(), chArgs)
        );

        LOG(log_.debug()) << "Made stub for remote.";
@@ -98,7 +89,7 @@ GrpcSource::fetchLedger(uint32_t sequence, bool getObjects, bool getObjectNeighb
    org::xrpl::rpc::v1::GetLedgerRequest request;
    grpc::ClientContext context;

-    context.set_deadline(std::chrono::system_clock::now() + deadline_);  // Prevent indefinite blocking
+    context.set_deadline(std::chrono::system_clock::now() + kDEADLINE);  // Prevent indefinite blocking

    request.mutable_ledger()->set_sequence(sequence);
    request.set_transactions(true);
@@ -109,7 +100,7 @@ GrpcSource::fetchLedger(uint32_t sequence, bool getObjects, bool getObjectNeighb

    grpc::Status const status = stub_->GetLedger(&context, request, &response);

-    if (status.ok() and not response.is_unlimited()) {
+    if (status.ok() && !response.is_unlimited()) {
        log_.warn() << "is_unlimited is false. Make sure secure_gateway is set correctly on the ETL source. Status = "
                    << status.error_message();
    }
@@ -117,46 +108,41 @@ GrpcSource::fetchLedger(uint32_t sequence, bool getObjects, bool getObjectNeighb
    return {status, std::move(response)};
 }

-InitialLedgerLoadResult
-GrpcSource::loadInitialLedger(
-    uint32_t const sequence,
-    uint32_t const numMarkers,
-    InitialLoadObserverInterface& observer
-)
+std::pair<std::vector<std::string>, bool>
+GrpcSource::loadInitialLedger(uint32_t const sequence, uint32_t const numMarkers)
 {
-    if (*initialLoadShouldStop_)
-        return std::unexpected{InitialLedgerLoadError::Cancelled};
-
    if (!stub_)
-        return std::unexpected{InitialLedgerLoadError::Errored};
+        return {{}, false};

-    std::vector<AsyncGrpcCall> calls = AsyncGrpcCall::makeAsyncCalls(sequence, numMarkers);
+    std::vector<etl::impl::AsyncCallData> calls = impl::makeAsyncCallData(sequence, numMarkers);

    LOG(log_.debug()) << "Starting data download for ledger " << sequence << ".";

-    grpc::CompletionQueue queue;
-    for (auto& call : calls)
-        call.call(stub_, queue);
+    grpc::CompletionQueue cq;
+    for (auto& c : calls)
+        c.call(stub_, cq);

-    std::vector<std::string> edgeKeys;
    void* tag = nullptr;
    bool ok = false;
-    bool abort = false;
    size_t numFinished = 0;
+    bool abort = false;
+    size_t const incr = 500000;
+    size_t progress = incr;
+    std::vector<std::string> edgeKeys;

-    while (numFinished < calls.size() && queue.Next(&tag, &ok)) {
+    while (numFinished < calls.size() && cq.Next(&tag, &ok)) {
        ASSERT(tag != nullptr, "Tag can't be null.");
-        auto ptr = static_cast<AsyncGrpcCall*>(tag);
+        auto ptr = static_cast<etl::impl::AsyncCallData*>(tag);

-        if (not ok or *initialLoadShouldStop_) {
-            LOG(log_.error()) << "loadInitialLedger cancelled";
-            return std::unexpected{InitialLedgerLoadError::Cancelled};
+        if (!ok) {
+            LOG(log_.error()) << "loadInitialLedger - ok is false";
+            return {{}, false};  // handle cancelled
        }

        LOG(log_.trace()) << "Marker prefix = " << ptr->getMarkerPrefix();

-        auto result = ptr->process(stub_, queue, observer, abort);
-        if (result != AsyncGrpcCall::CallStatus::More) {
+        auto result = ptr->process(stub_, cq, *backend_, abort);
+        if (result != etl::impl::AsyncCallData::CallStatus::MORE) {
            ++numFinished;
            LOG(log_.debug()) << "Finished a marker. Current number of finished = " << numFinished;

@@ -164,20 +150,18 @@ GrpcSource::loadInitialLedger(
                edgeKeys.push_back(std::move(lastKey));
        }

-        if (result == AsyncGrpcCall::CallStatus::Errored)
+        if (result == etl::impl::AsyncCallData::CallStatus::ERRORED)
            abort = true;
+
+        if (backend_->cache().size() > progress) {
+            LOG(log_.info()) << "Downloaded " << backend_->cache().size() << " records from rippled";
+            progress += incr;
+        }
    }

-    if (abort)
-        return std::unexpected{InitialLedgerLoadError::Errored};
-
-    return edgeKeys;
-}
-
-void
-GrpcSource::stop(boost::asio::yield_context)
-{
-    initialLoadShouldStop_->store(true);
+    LOG(log_.info()) << "Finished loadInitialLedger. cache size = " << backend_->cache().size() << ", abort = " << abort
+                     << ".";
+    return {std::move(edgeKeys), !abort};
 }

 }  // namespace etl::impl
--- a/src/etl/impl/GrpcSource.hpp
+++ b/src/etl/impl/GrpcSource.hpp
@@ -19,29 +19,25 @@

 #pragma once

-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
+#include "data/BackendInterface.hpp"
 #include "util/log/Logger.hpp"

-#include <boost/asio/spawn.hpp>
 #include <grpcpp/support/status.h>
 #include <org/xrpl/rpc/v1/get_ledger.pb.h>
 #include <xrpl/proto/org/xrpl/rpc/v1/xrp_ledger.grpc.pb.h>

-#include <atomic>
 #include <chrono>
 #include <cstdint>
 #include <memory>
 #include <string>
 #include <utility>
-
+#include <vector>
 namespace etl::impl {

 class GrpcSource {
    util::Logger log_;
    std::unique_ptr<org::xrpl::rpc::v1::XRPLedgerAPIService::Stub> stub_;
-    std::unique_ptr<std::atomic_bool> initialLoadShouldStop_;
-    std::chrono::system_clock::duration deadline_;
+    std::shared_ptr<BackendInterface> backend_;

    static constexpr auto kKEEPALIVE_PING_INTERVAL_MS = 10000;
    static constexpr auto kKEEPALIVE_TIMEOUT_MS = 5000;
@@ -50,11 +46,7 @@ class GrpcSource {
    static constexpr auto kDEADLINE = std::chrono::seconds(30);

 public:
-    GrpcSource(
-        std::string const& ip,
-        std::string const& grpcPort,
-        std::chrono::system_clock::duration deadline = kDEADLINE
-    );
+    GrpcSource(std::string const& ip, std::string const& grpcPort, std::shared_ptr<BackendInterface> backend);

    /**
     * @brief Fetch data for a specific ledger.
@@ -75,19 +67,10 @@ public:
     *
     * @param sequence Sequence of the ledger to download
     * @param numMarkers Number of markers to generate for async calls
-     * @param observer InitialLoadObserverInterface implementation
-     * @return Downloaded data or an indication of error or cancellation
+     * @return A std::pair of the data and a bool indicating whether the download was successful
     */
-    InitialLedgerLoadResult
-    loadInitialLedger(uint32_t sequence, uint32_t numMarkers, InitialLoadObserverInterface& observer);
-
-    /**
-     * @brief Stop any ongoing operations
-     * @note This is used to cancel any ongoing initial ledger downloads
-     * @param yield The coroutine context
-     */
-    void
-    stop(boost::asio::yield_context yield);
+    std::pair<std::vector<std::string>, bool>
+    loadInitialLedger(uint32_t sequence, uint32_t numMarkers);
 };

 }  // namespace etl::impl
--- a/src/etl/impl/LedgerFetcher.hpp
+++ b/src/etl/impl/LedgerFetcher.hpp
@@ -21,7 +21,7 @@

 #include "data/BackendInterface.hpp"
 #include "etl/LedgerFetcherInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
 #include "util/log/Logger.hpp"

 #include <grpcpp/grpcpp.h>
@@ -41,13 +41,13 @@ private:
    util::Logger log_{"ETL"};

    std::shared_ptr<BackendInterface> backend_;
-    std::shared_ptr<LoadBalancerInterface> loadBalancer_;
+    std::shared_ptr<etlng::LoadBalancerInterface> loadBalancer_;

 public:
    /**
     * @brief Create an instance of the fetcher
     */
-    LedgerFetcher(std::shared_ptr<BackendInterface> backend, std::shared_ptr<LoadBalancerInterface> balancer)
+    LedgerFetcher(std::shared_ptr<BackendInterface> backend, std::shared_ptr<etlng::LoadBalancerInterface> balancer)
        : backend_(std::move(backend)), loadBalancer_(std::move(balancer))
    {
    }
--- a/src/etl/impl/LedgerLoader.hpp
+++ b/src/etl/impl/LedgerLoader.hpp
@@ -0,0 +1,276 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "data/BackendInterface.hpp"
+#include "data/DBHelpers.hpp"
+#include "data/Types.hpp"
+#include "etl/MPTHelpers.hpp"
+#include "etl/NFTHelpers.hpp"
+#include "etl/SystemState.hpp"
+#include "etl/impl/LedgerFetcher.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
+#include "util/Assert.hpp"
+#include "util/LedgerUtils.hpp"
+#include "util/Profiler.hpp"
+#include "util/log/Logger.hpp"
+
+#include <xrpl/basics/base_uint.h>
+#include <xrpl/basics/strHex.h>
+#include <xrpl/beast/core/CurrentThreadName.h>
+#include <xrpl/protocol/LedgerHeader.h>
+#include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/Serializer.h>
+#include <xrpl/protocol/TxMeta.h>
+
+#include <chrono>
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <memory>
+#include <optional>
+#include <string>
+#include <utility>
+#include <vector>
+
+/**
+ * @brief Account transactions, NFT transactions and NFT data bundled togeher.
+ */
+struct FormattedTransactionsData {
+    std::vector<AccountTransactionsData> accountTxData;
+    std::vector<NFTTransactionsData> nfTokenTxData;
+    std::vector<NFTsData> nfTokensData;
+    std::vector<MPTHolderData> mptHoldersData;
+    std::vector<NFTsData> nfTokenURIChanges;
+};
+
+namespace etl::impl {
+
+/**
+ * @brief Loads ledger data into the DB
+ */
+template <typename LedgerFetcherType>
+class LedgerLoader {
+public:
+    using GetLedgerResponseType = etlng::LoadBalancerInterface::GetLedgerResponseType;
+    using OptionalGetLedgerResponseType = etlng::LoadBalancerInterface::OptionalGetLedgerResponseType;
+    using RawLedgerObjectType = etlng::LoadBalancerInterface::RawLedgerObjectType;
+
+private:
+    util::Logger log_{"ETL"};
+
+    std::shared_ptr<BackendInterface> backend_;
+    std::shared_ptr<etlng::LoadBalancerInterface> loadBalancer_;
+    std::reference_wrapper<LedgerFetcherType> fetcher_;
+    std::reference_wrapper<SystemState const> state_;  // shared state for ETL
+
+public:
+    /**
+     * @brief Create an instance of the loader
+     */
+    LedgerLoader(
+        std::shared_ptr<BackendInterface> backend,
+        std::shared_ptr<etlng::LoadBalancerInterface> balancer,
+        LedgerFetcherType& fetcher,
+        SystemState const& state
+    )
+        : backend_{std::move(backend)}
+        , loadBalancer_{std::move(balancer)}
+        , fetcher_{std::ref(fetcher)}
+        , state_{std::cref(state)}
+    {
+    }
+
+    /**
+     * @brief Insert extracted transaction into the ledger
+     *
+     * Insert all of the extracted transactions into the ledger, returning transactions related to accounts,
+     * transactions related to NFTs, and NFTs themselves for later processing.
+     *
+     * @param ledger ledger to insert transactions into
+     * @param data data extracted from an ETL source
+     * @return The necessary info to write the account_transactions/account_tx and nft_token_transactions tables
+     */
+    FormattedTransactionsData
+    insertTransactions(ripple::LedgerHeader const& ledger, GetLedgerResponseType& data)
+    {
+        FormattedTransactionsData result;
+
+        std::vector<NFTsData> nfTokenURIChanges;
+        for (auto& txn : *(data.mutable_transactions_list()->mutable_transactions())) {
+            std::string* raw = txn.mutable_transaction_blob();
+
+            ripple::SerialIter it{raw->data(), raw->size()};
+            ripple::STTx const sttx{it};
+
+            LOG(log_.trace()) << "Inserting transaction = " << sttx.getTransactionID();
+
+            ripple::TxMeta const txMeta{sttx.getTransactionID(), ledger.seq, txn.metadata_blob()};
+
+            auto const [nftTxs, maybeNFT] = getNFTDataFromTx(txMeta, sttx);
+            result.nfTokenTxData.insert(result.nfTokenTxData.end(), nftTxs.begin(), nftTxs.end());
+
+            // We need to unique the URI changes separately, in case the URI changes are discarded
+            if (maybeNFT) {
+                if (maybeNFT->onlyUriChanged) {
+                    nfTokenURIChanges.push_back(*maybeNFT);
+                } else {
+                    result.nfTokensData.push_back(*maybeNFT);
+                }
+            }
+
+            auto const maybeMPTHolder = getMPTHolderFromTx(txMeta, sttx);
+            if (maybeMPTHolder)
+                result.mptHoldersData.push_back(*maybeMPTHolder);
+
+            result.accountTxData.emplace_back(txMeta, sttx.getTransactionID());
+            static constexpr std::size_t kEY_SIZE = 32;
+            std::string keyStr{reinterpret_cast<char const*>(sttx.getTransactionID().data()), kEY_SIZE};
+            backend_->writeTransaction(
+                std::move(keyStr),
+                ledger.seq,
+                ledger.closeTime.time_since_epoch().count(),
+                std::move(*raw),
+                std::move(*txn.mutable_metadata_blob())
+            );
+        }
+
+        result.nfTokensData = getUniqueNFTsDatas(result.nfTokensData);
+        nfTokenURIChanges = getUniqueNFTsDatas(nfTokenURIChanges);
+
+        // Put uri change at the end to ensure the uri not overwritten
+        result.nfTokensData.insert(result.nfTokensData.end(), nfTokenURIChanges.begin(), nfTokenURIChanges.end());
+        return result;
+    }
+
+    /**
+     * @brief Download a ledger with specified sequence in full
+     *
+     * Note: This takes several minutes or longer.
+     *
+     * @param sequence the sequence of the ledger to download
+     * @return The ledger downloaded, with a full transaction and account state map
+     */
+    std::optional<ripple::LedgerHeader>
+    loadInitialLedger(uint32_t sequence)
+    {
+        // check that database is actually empty
+        auto rng = backend_->hardFetchLedgerRangeNoThrow();
+        if (rng) {
+            ASSERT(false, "Database is not empty");
+            return {};
+        }
+
+        // Fetch the ledger from the network. This function will not return until either the fetch is successful, or the
+        // server is being shutdown. This only fetches the ledger header and the transactions+metadata
+        OptionalGetLedgerResponseType ledgerData{fetcher_.get().fetchData(sequence)};
+        if (!ledgerData)
+            return {};
+
+        ripple::LedgerHeader lgrInfo = ::util::deserializeHeader(ripple::makeSlice(ledgerData->ledger_header()));
+
+        LOG(log_.debug()) << "Deserialized ledger header. " << ::util::toString(lgrInfo);
+
+        auto timeDiff = ::util::timed<std::chrono::duration<double>>([this, sequence, &lgrInfo, &ledgerData]() {
+            backend_->startWrites();
+
+            LOG(log_.debug()) << "Started writes";
+
+            backend_->writeLedger(lgrInfo, std::move(*ledgerData->mutable_ledger_header()));
+
+            LOG(log_.debug()) << "Wrote ledger";
+            FormattedTransactionsData insertTxResult = insertTransactions(lgrInfo, *ledgerData);
+            LOG(log_.debug()) << "Inserted txns";
+
+            // download the full account state map. This function downloads full
+            // ledger data and pushes the downloaded data into the writeQueue.
+            // asyncWriter consumes from the queue and inserts the data into the
+            // Ledger object. Once the below call returns, all data has been pushed
+            // into the queue
+            auto edgeKeys = loadBalancer_->loadInitialLedger(sequence);
+
+            size_t numWrites = 0;
+            backend_->cache().setFull();
+
+            auto seconds =
+                ::util::timed<std::chrono::seconds>([this, keys = std::move(edgeKeys), sequence, &numWrites]() mutable {
+                    for (auto& key : keys) {
+                        LOG(log_.debug()) << "Writing edge key = " << ripple::strHex(key);
+                        auto succ = backend_->cache().getSuccessor(*ripple::uint256::fromVoidChecked(key), sequence);
+                        if (succ)
+                            backend_->writeSuccessor(std::move(key), sequence, uint256ToString(succ->key));
+                    }
+
+                    ripple::uint256 prev = data::kFIRST_KEY;
+                    while (auto cur = backend_->cache().getSuccessor(prev, sequence)) {
+                        ASSERT(cur.has_value(), "Successor for key {} must exist", ripple::strHex(prev));
+                        if (prev == data::kFIRST_KEY)
+                            backend_->writeSuccessor(uint256ToString(prev), sequence, uint256ToString(cur->key));
+
+                        if (isBookDir(cur->key, cur->blob)) {
+                            auto base = getBookBase(cur->key);
+                            // make sure the base is not an actual object
+                            if (!backend_->cache().get(base, sequence)) {
+                                auto succ = backend_->cache().getSuccessor(base, sequence);
+                                ASSERT(succ.has_value(), "Book base {} must have a successor", ripple::strHex(base));
+                                if (succ->key == cur->key) {
+                                    LOG(log_.debug()) << "Writing book successor = " << ripple::strHex(base) << " - "
+                                                      << ripple::strHex(cur->key);
+
+                                    backend_->writeSuccessor(
+                                        uint256ToString(base), sequence, uint256ToString(cur->key)
+                                    );
+                                }
+                            }
+
+                            ++numWrites;
+                        }
+
+                        prev = cur->key;
+                        static constexpr std::size_t kLOG_STRIDE = 100000;
+                        if (numWrites % kLOG_STRIDE == 0 && numWrites != 0)
+                            LOG(log_.info()) << "Wrote " << numWrites << " book successors";
+                    }
+
+                    backend_->writeSuccessor(uint256ToString(prev), sequence, uint256ToString(data::kLAST_KEY));
+                    ++numWrites;
+                });
+
+            LOG(log_.info()) << "Looping through cache and submitting all writes took " << seconds
+                             << " seconds. numWrites = " << std::to_string(numWrites);
+
+            LOG(log_.debug()) << "Loaded initial ledger";
+
+            if (not state_.get().isStopping) {
+                backend_->writeAccountTransactions(std::move(insertTxResult.accountTxData));
+                backend_->writeNFTs(insertTxResult.nfTokensData);
+                backend_->writeNFTTransactions(insertTxResult.nfTokenTxData);
+                backend_->writeMPTHolders(insertTxResult.mptHoldersData);
+            }
+
+            backend_->finishWrites(sequence);
+        });
+
+        LOG(log_.debug()) << "Time to download and store ledger = " << timeDiff;
+        return lgrInfo;
+    }
+};
+
+}  // namespace etl::impl
--- a/src/etl/impl/LedgerPublisher.hpp
+++ b/src/etl/impl/LedgerPublisher.hpp
@@ -1,7 +1,7 @@
 //------------------------------------------------------------------------------
 /*
    This file is part of clio: https://github.com/XRPLF/clio
-    Copyright (c) 2025, the clio developers.
+    Copyright (c) 2023, the clio developers.

    Permission to use, copy, modify, and distribute this software for any
    purpose with or without fee is hereby granted, provided that the above
@@ -21,14 +21,12 @@

 #include "data/BackendInterface.hpp"
 #include "data/DBHelpers.hpp"
-#include "etl/LedgerPublisherInterface.hpp"
+#include "data/LedgerCacheInterface.hpp"
+#include "data/Types.hpp"
 #include "etl/SystemState.hpp"
-#include "etl/impl/Loading.hpp"
+#include "etlng/LedgerPublisherInterface.hpp"
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "util/Assert.hpp"
-#include "util/Mutex.hpp"
-#include "util/async/AnyExecutionContext.hpp"
-#include "util/async/AnyStrand.hpp"
 #include "util/log/Logger.hpp"
 #include "util/prometheus/Counter.hpp"
 #include "util/prometheus/Prometheus.hpp"
@@ -36,7 +34,6 @@
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/post.hpp>
 #include <boost/asio/strand.hpp>
-#include <fmt/format.h>
 #include <xrpl/basics/chrono.h>
 #include <xrpl/protocol/Fees.h>
 #include <xrpl/protocol/LedgerHeader.h>
@@ -71,16 +68,18 @@ namespace etl::impl {
 * includes reading all of the transactions from the database) is done from the application wide asio io_service, and a
 * strand is used to ensure ledgers are published in order.
 */
-class LedgerPublisher : public LedgerPublisherInterface {
+class LedgerPublisher : public etlng::LedgerPublisherInterface {
    util::Logger log_{"ETL"};

-    util::async::AnyStrand publishStrand_;
+    boost::asio::strand<boost::asio::io_context::executor_type> publishStrand_;

    std::shared_ptr<BackendInterface> backend_;
+    std::reference_wrapper<data::LedgerCacheInterface> cache_;
    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions_;
    std::reference_wrapper<SystemState const> state_;  // shared state for ETL

-    util::Mutex<std::chrono::time_point<ripple::NetClock>, std::shared_mutex> lastCloseTime_;
+    std::chrono::time_point<ripple::NetClock> lastCloseTime_;
+    mutable std::shared_mutex closeTimeMtx_;

    std::reference_wrapper<util::prometheus::CounterInt> lastPublishSeconds_ = PrometheusService::counterInt(
        "etl_last_publish_seconds",
@@ -88,20 +87,23 @@ class LedgerPublisher : public LedgerPublisherInterface {
        "Seconds since epoch of the last published ledger"
    );

-    util::Mutex<std::optional<uint32_t>, std::shared_mutex> lastPublishedSequence_;
+    std::optional<uint32_t> lastPublishedSequence_;
+    mutable std::shared_mutex lastPublishedSeqMtx_;

 public:
    /**
     * @brief Create an instance of the publisher
     */
    LedgerPublisher(
-        util::async::AnyExecutionContext ctx,
+        boost::asio::io_context& ioc,
        std::shared_ptr<BackendInterface> backend,
+        data::LedgerCacheInterface& cache,
        std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
        SystemState const& state
    )
-        : publishStrand_{ctx.makeStrand()}
+        : publishStrand_{boost::asio::make_strand(ioc)}
        , backend_{std::move(backend)}
+        , cache_{cache}
        , subscriptions_{std::move(subscriptions)}
        , state_{std::cref(state)}
    {
@@ -163,13 +165,28 @@ public:
    void
    publish(ripple::LedgerHeader const& lgrInfo)
    {
-        publishStrand_.submit([this, lgrInfo = lgrInfo] {
+        boost::asio::post(publishStrand_, [this, lgrInfo = lgrInfo]() {
            LOG(log_.info()) << "Publishing ledger " << std::to_string(lgrInfo.seq);

+            if (!state_.get().isWriting) {
+                LOG(log_.info()) << "Updating ledger range for read node.";
+
+                if (!cache_.get().isDisabled()) {
+                    std::vector<data::LedgerObject> const diff = data::synchronousAndRetryOnTimeout([&](auto yield) {
+                        return backend_->fetchLedgerDiff(lgrInfo.seq, yield);
+                    });
+
+                    cache_.get().update(diff, lgrInfo.seq);
+                }
+
+                backend_->updateRange(lgrInfo.seq);
+            }
+
            setLastClose(lgrInfo.closeTime);
            auto age = lastCloseAgeSeconds();

            // if the ledger closed over MAX_LEDGER_AGE_SECONDS ago, assume we are still catching up and don't publish
+            // TODO: this probably should be a strategy
            static constexpr std::uint32_t kMAX_LEDGER_AGE_SECONDS = 600;
            if (age < kMAX_LEDGER_AGE_SECONDS) {
                std::optional<ripple::Fees> fees = data::synchronousAndRetryOnTimeout([&](auto yield) {
@@ -177,14 +194,17 @@ public:
                });
                ASSERT(fees.has_value(), "Fees must exist for ledger {}", lgrInfo.seq);

-                auto transactions = data::synchronousAndRetryOnTimeout([&](auto yield) {
-                    return backend_->fetchAllTransactionsInLedger(lgrInfo.seq, yield);
-                });
+                std::vector<data::TransactionAndMetadata> transactions =
+                    data::synchronousAndRetryOnTimeout([&](auto yield) {
+                        return backend_->fetchAllTransactionsInLedger(lgrInfo.seq, yield);
+                    });

                auto const ledgerRange = backend_->fetchLedgerRange();
                ASSERT(ledgerRange.has_value(), "Ledger range must exist");

-                auto const range = fmt::format("{}-{}", ledgerRange->minSequence, ledgerRange->maxSequence);
+                std::string const range =
+                    std::to_string(ledgerRange->minSequence) + "-" + std::to_string(ledgerRange->maxSequence);
+
                subscriptions_->pubLedger(lgrInfo, *fees, range, transactions.size());

                // order with transaction index
@@ -197,15 +217,15 @@ public:
                        object2.getFieldU32(ripple::sfTransactionIndex);
                });

-                for (auto const& txAndMeta : transactions)
+                for (auto& txAndMeta : transactions)
                    subscriptions_->pubTransaction(txAndMeta, lgrInfo);

                subscriptions_->pubBookChanges(lgrInfo, transactions);

                setLastPublishTime();
-                LOG(log_.info()) << "Published ledger " << lgrInfo.seq;
+                LOG(log_.info()) << "Published ledger " << std::to_string(lgrInfo.seq);
            } else {
-                LOG(log_.info()) << "Skipping publishing ledger " << lgrInfo.seq;
+                LOG(log_.info()) << "Skipping publishing ledger " << std::to_string(lgrInfo.seq);
            }
        });

@@ -240,30 +260,32 @@ public:
    std::uint32_t
    lastCloseAgeSeconds() const override
    {
-        auto closeTime = lastCloseTime_.lock()->time_since_epoch().count();
+        std::shared_lock const lck(closeTimeMtx_);
        auto now = std::chrono::duration_cast<std::chrono::seconds>(std::chrono::system_clock::now().time_since_epoch())
                       .count();
+        auto closeTime = lastCloseTime_.time_since_epoch().count();
        if (now < (kRIPPLE_EPOCH_START + closeTime))
            return 0;
        return now - (kRIPPLE_EPOCH_START + closeTime);
    }

    /**
-     * @brief Get the sequence of the last schueduled ledger to publish, Be aware that the ledger may not have been
+     * @brief Get the sequence of the last scheduled ledger to publish, Be aware that the ledger may not have been
     * published to network
     */
    std::optional<uint32_t>
    getLastPublishedSequence() const
    {
-        return *lastPublishedSequence_.lock();
+        std::scoped_lock const lck(lastPublishedSeqMtx_);
+        return lastPublishedSequence_;
    }

 private:
    void
    setLastClose(std::chrono::time_point<ripple::NetClock> lastCloseTime)
    {
-        auto closeTime = lastCloseTime_.lock<std::scoped_lock>();
-        *closeTime = lastCloseTime;
+        std::scoped_lock const lck(closeTimeMtx_);
+        lastCloseTime_ = lastCloseTime;
    }

    void
@@ -277,8 +299,8 @@ private:
    void
    setLastPublishedSequence(std::optional<uint32_t> lastPublishedSequence)
    {
-        auto lastPublishSeq = lastPublishedSequence_.lock();
-        *lastPublishSeq = lastPublishedSequence;
+        std::scoped_lock const lck(lastPublishedSeqMtx_);
+        lastPublishedSequence_ = lastPublishedSequence;
    }
 };

--- a/src/etl/impl/SourceImpl.hpp
+++ b/src/etl/impl/SourceImpl.hpp
@@ -19,8 +19,6 @@

 #pragma once

-#include "etl/InitialLoadObserverInterface.hpp"
-#include "etl/LoadBalancerInterface.hpp"
 #include "etl/Source.hpp"
 #include "etl/impl/ForwardingSource.hpp"
 #include "etl/impl/GrpcSource.hpp"
@@ -53,8 +51,8 @@ namespace etl::impl {
 */
 template <
    typename GrpcSourceType = GrpcSource,
-    typename SubscriptionSourceTypePtr = std::unique_ptr<impl::SubscriptionSource>,
-    typename ForwardingSourceType = impl::ForwardingSource>
+    typename SubscriptionSourceTypePtr = std::unique_ptr<SubscriptionSource>,
+    typename ForwardingSourceType = ForwardingSource>
 class SourceImpl : public SourceBase {
    std::string ip_;
    std::string wsPort_;
@@ -108,7 +106,6 @@ public:
    stop(boost::asio::yield_context yield) final
    {
        subscriptionSource_->stop(yield);
-        grpcSource_.stop(yield);
    }

    /**
@@ -201,13 +198,12 @@ public:
     *
     * @param sequence Sequence of the ledger to download
     * @param numMarkers Number of markers to generate for async calls
-     * @param loader InitialLoadObserverInterface implementation
     * @return A std::pair of the data and a bool indicating whether the download was successful
     */
-    InitialLedgerLoadResult
-    loadInitialLedger(uint32_t sequence, std::uint32_t numMarkers, InitialLoadObserverInterface& loader) final
+    std::pair<std::vector<std::string>, bool>
+    loadInitialLedger(uint32_t sequence, std::uint32_t numMarkers) final
    {
-        return grpcSource_.loadInitialLedger(sequence, numMarkers, loader);
+        return grpcSource_.loadInitialLedger(sequence, numMarkers);
    }

    /**
--- a/src/etl/impl/Transformer.hpp
+++ b/src/etl/impl/Transformer.hpp
@@ -0,0 +1,424 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "data/BackendInterface.hpp"
+#include "data/DBHelpers.hpp"
+#include "data/Types.hpp"
+#include "etl/SystemState.hpp"
+#include "etl/impl/AmendmentBlockHandler.hpp"
+#include "etl/impl/LedgerLoader.hpp"
+#include "util/Assert.hpp"
+#include "util/LedgerUtils.hpp"
+#include "util/Profiler.hpp"
+#include "util/log/Logger.hpp"
+
+#include <grpcpp/grpcpp.h>
+#include <xrpl/basics/base_uint.h>
+#include <xrpl/basics/strHex.h>
+#include <xrpl/beast/core/CurrentThreadName.h>
+#include <xrpl/proto/org/xrpl/rpc/v1/xrp_ledger.grpc.pb.h>
+#include <xrpl/protocol/LedgerHeader.h>
+
+#include <chrono>
+#include <cstdint>
+#include <functional>
+#include <memory>
+#include <optional>
+#include <set>
+#include <stdexcept>
+#include <string>
+#include <thread>
+#include <utility>
+#include <vector>
+
+namespace etl::impl {
+
+/*
+ * TODO:
+ *
+ * 1) loading of data into db should not really be part of transform right?
+ * 2) can we just prepare the data and give it to the loader afterwards?
+ * 3) how to deal with cache update that is needed to write successors if neighbours not included?
+ */
+
+/**
+ * @brief Transformer thread that prepares new ledger out of raw data from GRPC.
+ */
+template <
+    typename DataPipeType,
+    typename LedgerLoaderType,
+    typename LedgerPublisherType,
+    typename AmendmentBlockHandlerType>
+class Transformer {
+    using GetLedgerResponseType = typename LedgerLoaderType::GetLedgerResponseType;
+    using RawLedgerObjectType = typename LedgerLoaderType::RawLedgerObjectType;
+
+    util::Logger log_{"ETL"};
+
+    std::reference_wrapper<DataPipeType> pipe_;
+    std::shared_ptr<BackendInterface> backend_;
+    std::reference_wrapper<LedgerLoaderType> loader_;
+    std::reference_wrapper<LedgerPublisherType> publisher_;
+    std::reference_wrapper<AmendmentBlockHandlerType> amendmentBlockHandler_;
+
+    uint32_t startSequence_;
+    std::reference_wrapper<SystemState> state_;  // shared state for ETL
+
+    std::thread thread_;
+
+public:
+    /**
+     * @brief Create an instance of the transformer.
+     *
+     * This spawns a new thread that reads from the data pipe and writes ledgers to the DB using LedgerLoader and
+     * LedgerPublisher.
+     */
+    Transformer(
+        DataPipeType& pipe,
+        std::shared_ptr<BackendInterface> backend,
+        LedgerLoaderType& loader,
+        LedgerPublisherType& publisher,
+        AmendmentBlockHandlerType& amendmentBlockHandler,
+        uint32_t startSequence,
+        SystemState& state
+    )
+        : pipe_{std::ref(pipe)}
+        , backend_{std::move(backend)}
+        , loader_{std::ref(loader)}
+        , publisher_{std::ref(publisher)}
+        , amendmentBlockHandler_{std::ref(amendmentBlockHandler)}
+        , startSequence_{startSequence}
+        , state_{std::ref(state)}
+    {
+        thread_ = std::thread([this]() { process(); });
+    }
+
+    /**
+     * @brief Joins the transformer thread.
+     */
+    ~Transformer()
+    {
+        if (thread_.joinable())
+            thread_.join();
+    }
+
+    /**
+     * @brief Block calling thread until transformer thread exits.
+     */
+    void
+    waitTillFinished()
+    {
+        ASSERT(thread_.joinable(), "Transformer thread must be joinable");
+        thread_.join();
+    }
+
+private:
+    void
+    process()
+    {
+        beast::setCurrentThreadName("ETLService transform");
+        uint32_t currentSequence = startSequence_;
+
+        while (not hasWriteConflict()) {
+            auto fetchResponse = pipe_.get().popNext(currentSequence);
+            ++currentSequence;
+
+            // if fetchResponse is an empty optional, the extractor thread has stopped and the transformer should
+            // stop as well
+            if (!fetchResponse)
+                break;
+
+            if (isStopping())
+                continue;
+
+            auto const start = std::chrono::system_clock::now();
+            auto [lgrInfo, success] = buildNextLedger(*fetchResponse);
+
+            if (success) {
+                auto const numTxns = fetchResponse->transactions_list().transactions_size();
+                auto const numObjects = fetchResponse->ledger_objects().objects_size();
+                auto const end = std::chrono::system_clock::now();
+                auto const duration = ((end - start).count()) / 1000000000.0;
+
+                LOG(log_.info()) << "Load phase of ETL. Successfully wrote ledger! Ledger info: "
+                                 << util::toString(lgrInfo) << ". txn count = " << numTxns
+                                 << ". object count = " << numObjects << ". load time = " << duration
+                                 << ". load txns per second = " << numTxns / duration
+                                 << ". load objs per second = " << numObjects / duration;
+
+                // success is false if the ledger was already written
+                publisher_.get().publish(lgrInfo);
+            } else {
+                LOG(log_.error()) << "Error writing ledger. " << util::toString(lgrInfo);
+            }
+
+            setWriteConflict(not success);
+        }
+    }
+
+    /**
+     * @brief Build the next ledger using the previous ledger and the extracted data.
+     * @note rawData should be data that corresponds to the ledger immediately following the previous seq.
+     *
+     * @param rawData Data extracted from an ETL source
+     * @return The newly built ledger and data to write to the database
+     */
+    std::pair<ripple::LedgerHeader, bool>
+    buildNextLedger(GetLedgerResponseType& rawData)
+    {
+        LOG(log_.debug()) << "Beginning ledger update";
+        ripple::LedgerHeader lgrInfo = ::util::deserializeHeader(ripple::makeSlice(rawData.ledger_header()));
+
+        LOG(log_.debug()) << "Deserialized ledger header. " << ::util::toString(lgrInfo);
+        backend_->startWrites();
+        backend_->writeLedger(lgrInfo, std::move(*rawData.mutable_ledger_header()));
+
+        writeSuccessors(lgrInfo, rawData);
+        std::optional<FormattedTransactionsData> insertTxResultOp;
+        try {
+            updateCache(lgrInfo, rawData);
+
+            LOG(log_.debug()) << "Inserted/modified/deleted all objects. Number of objects = "
+                              << rawData.ledger_objects().objects_size();
+
+            insertTxResultOp.emplace(loader_.get().insertTransactions(lgrInfo, rawData));
+        } catch (std::runtime_error const& e) {
+            LOG(log_.fatal()) << "Failed to build next ledger: " << e.what();
+
+            amendmentBlockHandler_.get().notifyAmendmentBlocked();
+            return {ripple::LedgerHeader{}, false};
+        }
+
+        LOG(log_.debug()) << "Inserted all transactions. Number of transactions  = "
+                          << rawData.transactions_list().transactions_size();
+
+        backend_->writeAccountTransactions(std::move(insertTxResultOp->accountTxData));
+        backend_->writeNFTs(insertTxResultOp->nfTokensData);
+        backend_->writeNFTTransactions(insertTxResultOp->nfTokenTxData);
+        backend_->writeMPTHolders(insertTxResultOp->mptHoldersData);
+
+        auto [success, duration] =
+            ::util::timed<std::chrono::duration<double>>([&]() { return backend_->finishWrites(lgrInfo.seq); });
+
+        LOG(log_.debug()) << "Finished writes. Total time: " << std::to_string(duration);
+        LOG(log_.debug()) << "Finished ledger update: " << ::util::toString(lgrInfo);
+
+        return {lgrInfo, success};
+    }
+
+    /**
+     * @brief Update cache from new ledger data.
+     *
+     * @param lgrInfo Ledger info
+     * @param rawData Ledger data from GRPC
+     */
+    void
+    updateCache(ripple::LedgerHeader const& lgrInfo, GetLedgerResponseType& rawData)
+    {
+        std::vector<data::LedgerObject> cacheUpdates;
+        cacheUpdates.reserve(rawData.ledger_objects().objects_size());
+
+        // TODO change these to unordered_set
+        std::set<ripple::uint256> bookSuccessorsToCalculate;
+        std::set<ripple::uint256> modified;
+
+        for (auto& obj : *(rawData.mutable_ledger_objects()->mutable_objects())) {
+            auto key = ripple::uint256::fromVoidChecked(obj.key());
+            ASSERT(key.has_value(), "Failed to deserialize key from void");
+
+            cacheUpdates.push_back({*key, {obj.mutable_data()->begin(), obj.mutable_data()->end()}});
+            LOG(log_.debug()) << "key = " << ripple::strHex(*key) << " - mod type = " << obj.mod_type();
+
+            if (obj.mod_type() != RawLedgerObjectType::MODIFIED && !rawData.object_neighbors_included()) {
+                LOG(log_.debug()) << "object neighbors not included. using cache";
+
+                if (!backend_->cache().isFull() || backend_->cache().latestLedgerSequence() != lgrInfo.seq - 1)
+                    throw std::logic_error("Cache is not full, but object neighbors were not included");
+
+                auto const blob = obj.mutable_data();
+                auto checkBookBase = false;
+                auto const isDeleted = (blob->size() == 0);
+
+                if (isDeleted) {
+                    auto const old = backend_->cache().get(*key, lgrInfo.seq - 1);
+                    ASSERT(old.has_value(), "Deleted object {} must be in cache", ripple::strHex(*key));
+                    checkBookBase = isBookDir(*key, *old);
+                } else {
+                    checkBookBase = isBookDir(*key, *blob);
+                }
+
+                if (checkBookBase) {
+                    LOG(log_.debug()) << "Is book dir. Key = " << ripple::strHex(*key);
+
+                    auto const bookBase = getBookBase(*key);
+                    auto const oldFirstDir = backend_->cache().getSuccessor(bookBase, lgrInfo.seq - 1);
+                    ASSERT(
+                        oldFirstDir.has_value(),
+                        "Book base must have a successor for lgrInfo.seq - 1 = {}",
+                        lgrInfo.seq - 1
+                    );
+
+                    // We deleted the first directory, or we added a directory prior to the old first
+                    // directory
+                    if ((isDeleted && key == oldFirstDir->key) || (!isDeleted && key < oldFirstDir->key)) {
+                        LOG(log_.debug())
+                            << "Need to recalculate book base successor. base = " << ripple::strHex(bookBase)
+                            << " - key = " << ripple::strHex(*key) << " - isDeleted = " << isDeleted
+                            << " - seq = " << lgrInfo.seq;
+                        bookSuccessorsToCalculate.insert(bookBase);
+                    }
+                }
+            }
+
+            if (obj.mod_type() == RawLedgerObjectType::MODIFIED)
+                modified.insert(*key);
+
+            backend_->writeLedgerObject(std::move(*obj.mutable_key()), lgrInfo.seq, std::move(*obj.mutable_data()));
+        }
+
+        backend_->cache().update(cacheUpdates, lgrInfo.seq);
+
+        // rippled didn't send successor information, so use our cache
+        if (!rawData.object_neighbors_included()) {
+            LOG(log_.debug()) << "object neighbors not included. using cache";
+            if (!backend_->cache().isFull() || backend_->cache().latestLedgerSequence() != lgrInfo.seq)
+                throw std::logic_error("Cache is not full, but object neighbors were not included");
+
+            for (auto const& obj : cacheUpdates) {
+                if (modified.contains(obj.key))
+                    continue;
+
+                auto lb = backend_->cache().getPredecessor(obj.key, lgrInfo.seq);
+                if (!lb)
+                    lb = {.key = data::kFIRST_KEY, .blob = {}};
+
+                auto ub = backend_->cache().getSuccessor(obj.key, lgrInfo.seq);
+                if (!ub)
+                    ub = {.key = data::kLAST_KEY, .blob = {}};
+
+                if (obj.blob.empty()) {
+                    LOG(log_.debug()) << "writing successor for deleted object " << ripple::strHex(obj.key) << " - "
+                                      << ripple::strHex(lb->key) << " - " << ripple::strHex(ub->key);
+
+                    backend_->writeSuccessor(uint256ToString(lb->key), lgrInfo.seq, uint256ToString(ub->key));
+                } else {
+                    backend_->writeSuccessor(uint256ToString(lb->key), lgrInfo.seq, uint256ToString(obj.key));
+                    backend_->writeSuccessor(uint256ToString(obj.key), lgrInfo.seq, uint256ToString(ub->key));
+
+                    LOG(log_.debug()) << "writing successor for new object " << ripple::strHex(lb->key) << " - "
+                                      << ripple::strHex(obj.key) << " - " << ripple::strHex(ub->key);
+                }
+            }
+
+            for (auto const& base : bookSuccessorsToCalculate) {
+                auto succ = backend_->cache().getSuccessor(base, lgrInfo.seq);
+                if (succ) {
+                    backend_->writeSuccessor(uint256ToString(base), lgrInfo.seq, uint256ToString(succ->key));
+
+                    LOG(log_.debug()) << "Updating book successor " << ripple::strHex(base) << " - "
+                                      << ripple::strHex(succ->key);
+                } else {
+                    backend_->writeSuccessor(uint256ToString(base), lgrInfo.seq, uint256ToString(data::kLAST_KEY));
+
+                    LOG(log_.debug()) << "Updating book successor " << ripple::strHex(base) << " - "
+                                      << ripple::strHex(data::kLAST_KEY);
+                }
+            }
+        }
+    }
+
+    /**
+     * @brief Write successors info into DB.
+     *
+     * @param lgrInfo Ledger info
+     * @param rawData Ledger data from GRPC
+     */
+    void
+    writeSuccessors(ripple::LedgerHeader const& lgrInfo, GetLedgerResponseType& rawData)
+    {
+        // Write successor info, if included from rippled
+        if (rawData.object_neighbors_included()) {
+            LOG(log_.debug()) << "object neighbors included";
+
+            for (auto& obj : *(rawData.mutable_book_successors())) {
+                auto firstBook = std::move(*obj.mutable_first_book());
+                if (!firstBook.size())
+                    firstBook = uint256ToString(data::kLAST_KEY);
+                LOG(log_.debug()) << "writing book successor " << ripple::strHex(obj.book_base()) << " - "
+                                  << ripple::strHex(firstBook);
+
+                backend_->writeSuccessor(std::move(*obj.mutable_book_base()), lgrInfo.seq, std::move(firstBook));
+            }
+
+            for (auto& obj : *(rawData.mutable_ledger_objects()->mutable_objects())) {
+                if (obj.mod_type() != RawLedgerObjectType::MODIFIED) {
+                    std::string* predPtr = obj.mutable_predecessor();
+                    if (predPtr->empty())
+                        *predPtr = uint256ToString(data::kFIRST_KEY);
+                    std::string* succPtr = obj.mutable_successor();
+                    if (succPtr->empty())
+                        *succPtr = uint256ToString(data::kLAST_KEY);
+
+                    if (obj.mod_type() == RawLedgerObjectType::DELETED) {
+                        LOG(log_.debug()) << "Modifying successors for deleted object " << ripple::strHex(obj.key())
+                                          << " - " << ripple::strHex(*predPtr) << " - " << ripple::strHex(*succPtr);
+
+                        backend_->writeSuccessor(std::move(*predPtr), lgrInfo.seq, std::move(*succPtr));
+                    } else {
+                        LOG(log_.debug()) << "adding successor for new object " << ripple::strHex(obj.key()) << " - "
+                                          << ripple::strHex(*predPtr) << " - " << ripple::strHex(*succPtr);
+
+                        backend_->writeSuccessor(std::move(*predPtr), lgrInfo.seq, std::string{obj.key()});
+                        backend_->writeSuccessor(std::string{obj.key()}, lgrInfo.seq, std::move(*succPtr));
+                    }
+                } else
+                    LOG(log_.debug()) << "object modified " << ripple::strHex(obj.key());
+            }
+        }
+    }
+
+    /** @return true if the transformer is stopping; false otherwise */
+    bool
+    isStopping() const
+    {
+        return state_.get().isStopping;
+    }
+
+    /** @return true if there was a write conflict; false otherwise */
+    bool
+    hasWriteConflict() const
+    {
+        return state_.get().writeConflict;
+    }
+
+    /**
+     * @brief Sets the write conflict flag.
+     *
+     * @param conflict The value to set
+     */
+    void
+    setWriteConflict(bool conflict)
+    {
+        state_.get().writeConflict = conflict;
+    }
+};
+
+}  // namespace etl::impl
--- a/src/etlng/AmendmentBlockHandlerInterface.hpp
+++ b/src/etlng/AmendmentBlockHandlerInterface.hpp
@@ -19,7 +19,7 @@

 #pragma once

-namespace etl {
+namespace etlng {

 /**
 * @brief The interface of a handler for amendment blocking
@@ -40,4 +40,4 @@ struct AmendmentBlockHandlerInterface {
    stop() = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/CMakeLists.txt
+++ b/src/etlng/CMakeLists.txt
@@ -0,0 +1,23 @@
+add_library(clio_etlng)
+
+target_sources(
+  clio_etlng
+  PRIVATE ETLService.cpp
+          LoadBalancer.cpp
+          Source.cpp
+          impl/AmendmentBlockHandler.cpp
+          impl/AsyncGrpcCall.cpp
+          impl/Extraction.cpp
+          impl/GrpcSource.cpp
+          impl/ForwardingSource.cpp
+          impl/Loading.cpp
+          impl/Monitor.cpp
+          impl/TaskManager.cpp
+          impl/ext/Cache.cpp
+          impl/ext/Core.cpp
+          impl/ext/MPT.cpp
+          impl/ext/NFT.cpp
+          impl/ext/Successor.cpp
+)
+
+target_link_libraries(clio_etlng PUBLIC clio_data)
--- a/src/etlng/CacheLoaderInterface.hpp
+++ b/src/etlng/CacheLoaderInterface.hpp
@@ -21,7 +21,7 @@

 #include <cstdint>

-namespace etl {
+namespace etlng {

 /**
 * @brief An interface for the Cache Loader
@@ -50,4 +50,4 @@ struct CacheLoaderInterface {
    wait() noexcept = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/CacheUpdaterInterface.hpp
+++ b/src/etlng/CacheUpdaterInterface.hpp
@@ -20,12 +20,12 @@
 #pragma once

 #include "data/Types.hpp"
-#include "etl/Models.hpp"
+#include "etlng/Models.hpp"

 #include <cstdint>
 #include <vector>

-namespace etl {
+namespace etlng {

 /**
 * @brief An interface for the Cache Updater
@@ -63,4 +63,4 @@ struct CacheUpdaterInterface {
    setFull() = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/ETLService.cpp
+++ b/src/etlng/ETLService.cpp
@@ -0,0 +1,334 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2025, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "etlng/ETLService.hpp"
+
+#include "data/BackendInterface.hpp"
+#include "data/LedgerCacheInterface.hpp"
+#include "data/Types.hpp"
+#include "etl/ETLState.hpp"
+#include "etl/NetworkValidatedLedgersInterface.hpp"
+#include "etl/SystemState.hpp"
+#include "etl/impl/AmendmentBlockHandler.hpp"
+#include "etl/impl/LedgerFetcher.hpp"
+#include "etlng/CacheLoaderInterface.hpp"
+#include "etlng/CacheUpdaterInterface.hpp"
+#include "etlng/ExtractorInterface.hpp"
+#include "etlng/InitialLoadObserverInterface.hpp"
+#include "etlng/LedgerPublisherInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
+#include "etlng/LoaderInterface.hpp"
+#include "etlng/MonitorInterface.hpp"
+#include "etlng/MonitorProviderInterface.hpp"
+#include "etlng/TaskManagerProviderInterface.hpp"
+#include "etlng/impl/AmendmentBlockHandler.hpp"
+#include "etlng/impl/CacheUpdater.hpp"
+#include "etlng/impl/Extraction.hpp"
+#include "etlng/impl/LedgerPublisher.hpp"
+#include "etlng/impl/Loading.hpp"
+#include "etlng/impl/Registry.hpp"
+#include "etlng/impl/Scheduling.hpp"
+#include "etlng/impl/TaskManager.hpp"
+#include "etlng/impl/ext/Cache.hpp"
+#include "etlng/impl/ext/Core.hpp"
+#include "etlng/impl/ext/NFT.hpp"
+#include "etlng/impl/ext/Successor.hpp"
+#include "util/Assert.hpp"
+#include "util/Profiler.hpp"
+#include "util/async/AnyExecutionContext.hpp"
+#include "util/log/Logger.hpp"
+
+#include <boost/json/object.hpp>
+#include <boost/signals2/connection.hpp>
+#include <xrpl/protocol/LedgerHeader.h>
+
+#include <chrono>
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <memory>
+#include <optional>
+#include <string>
+#include <utility>
+
+namespace etlng {
+
+ETLService::ETLService(
+    util::async::AnyExecutionContext ctx,
+    std::reference_wrapper<util::config::ClioConfigDefinition const> config,
+    std::shared_ptr<data::BackendInterface> backend,
+    std::shared_ptr<LoadBalancerInterface> balancer,
+    std::shared_ptr<etl::NetworkValidatedLedgersInterface> ledgers,
+    std::shared_ptr<LedgerPublisherInterface> publisher,
+    std::shared_ptr<CacheLoaderInterface> cacheLoader,
+    std::shared_ptr<CacheUpdaterInterface> cacheUpdater,
+    std::shared_ptr<ExtractorInterface> extractor,
+    std::shared_ptr<LoaderInterface> loader,
+    std::shared_ptr<InitialLoadObserverInterface> initialLoadObserver,
+    std::shared_ptr<etlng::TaskManagerProviderInterface> taskManagerProvider,
+    std::shared_ptr<etlng::MonitorProviderInterface> monitorProvider,
+    std::shared_ptr<etl::SystemState> state
+)
+    : ctx_(std::move(ctx))
+    , config_(config)
+    , backend_(std::move(backend))
+    , balancer_(std::move(balancer))
+    , ledgers_(std::move(ledgers))
+    , publisher_(std::move(publisher))
+    , cacheLoader_(std::move(cacheLoader))
+    , cacheUpdater_(std::move(cacheUpdater))
+    , extractor_(std::move(extractor))
+    , loader_(std::move(loader))
+    , initialLoadObserver_(std::move(initialLoadObserver))
+    , taskManagerProvider_(std::move(taskManagerProvider))
+    , monitorProvider_(std::move(monitorProvider))
+    , state_(std::move(state))
+    , startSequence_(config.get().maybeValue<uint32_t>("start_sequence"))
+    , finishSequence_(config.get().maybeValue<uint32_t>("finish_sequence"))
+{
+    ASSERT(not state_->isWriting, "ETL should never start in writer mode");
+
+    if (startSequence_.has_value())
+        LOG(log_.info()) << "Start sequence: " << *startSequence_;
+
+    if (finishSequence_.has_value())
+        LOG(log_.info()) << "Finish sequence: " << *finishSequence_;
+
+    LOG(log_.info()) << "Starting in " << (state_->isStrictReadonly ? "STRICT READONLY MODE" : "WRITE MODE");
+}
+
+ETLService::~ETLService()
+{
+    stop();
+    LOG(log_.debug()) << "Destroying ETLng";
+}
+
+void
+ETLService::run()
+{
+    LOG(log_.info()) << "Running ETLng...";
+
+    mainLoop_.emplace(ctx_.execute([this] {
+        auto const rng = loadInitialLedgerIfNeeded();
+
+        LOG(log_.info()) << "Waiting for next ledger to be validated by network...";
+        std::optional<uint32_t> const mostRecentValidated = ledgers_->getMostRecent();
+
+        if (not mostRecentValidated) {
+            LOG(log_.info()) << "The wait for the next validated ledger has been aborted. "
+                                "Exiting monitor loop";
+            return;
+        }
+
+        if (not rng.has_value()) {
+            LOG(log_.warn()) << "Initial ledger download got cancelled - stopping ETL service";
+            return;
+        }
+
+        auto const nextSequence = rng->maxSequence + 1;
+
+        LOG(log_.debug()) << "Database is populated. Starting monitor loop. sequence = " << nextSequence;
+        startMonitor(nextSequence);
+
+        // If we are a writer as the result of loading the initial ledger - start loading
+        if (state_->isWriting)
+            startLoading(nextSequence);
+    }));
+}
+
+void
+ETLService::stop()
+{
+    LOG(log_.info()) << "Stop called";
+
+    if (mainLoop_)
+        mainLoop_->wait();
+    if (taskMan_)
+        taskMan_->stop();
+    if (monitor_)
+        monitor_->stop();
+}
+
+boost::json::object
+ETLService::getInfo() const
+{
+    boost::json::object result;
+
+    result["etl_sources"] = balancer_->toJson();
+    result["is_writer"] = static_cast<int>(state_->isWriting);
+    result["read_only"] = static_cast<int>(state_->isStrictReadonly);
+    auto last = publisher_->getLastPublish();
+    if (last.time_since_epoch().count() != 0)
+        result["last_publish_age_seconds"] = std::to_string(publisher_->lastPublishAgeSeconds());
+    return result;
+}
+
+bool
+ETLService::isAmendmentBlocked() const
+{
+    return state_->isAmendmentBlocked;
+}
+
+bool
+ETLService::isCorruptionDetected() const
+{
+    return state_->isCorruptionDetected;
+}
+
+std::optional<etl::ETLState>
+ETLService::getETLState() const
+{
+    return balancer_->getETLState();
+}
+
+std::uint32_t
+ETLService::lastCloseAgeSeconds() const
+{
+    return publisher_->lastCloseAgeSeconds();
+}
+
+std::optional<data::LedgerRange>
+ETLService::loadInitialLedgerIfNeeded()
+{
+    auto rng = backend_->hardFetchLedgerRangeNoThrow();
+    if (not rng.has_value()) {
+        ASSERT(
+            not state_->isStrictReadonly,
+            "Database is empty but this node is in strict readonly mode. Can't write initial ledger."
+        );
+
+        LOG(log_.info()) << "Database is empty. Will download a ledger from the network.";
+        state_->isWriting = true;  // immediately become writer as the db is empty
+
+        auto const getMostRecent = [this]() {
+            LOG(log_.info()) << "Waiting for next ledger to be validated by network...";
+            return ledgers_->getMostRecent();
+        };
+
+        if (auto const maybeSeq = startSequence_.or_else(getMostRecent); maybeSeq.has_value()) {
+            auto const seq = *maybeSeq;
+            LOG(log_.info()) << "Starting from sequence " << seq
+                             << ". Initial ledger download and extraction can take a while...";
+
+            auto [ledger, timeDiff] = ::util::timed<std::chrono::duration<double>>([this, seq]() {
+                return extractor_->extractLedgerOnly(seq).and_then(
+                    [this, seq](auto&& data) -> std::optional<ripple::LedgerHeader> {
+                        // TODO: loadInitialLedger in balancer should be called fetchEdgeKeys or similar
+                        auto res = balancer_->loadInitialLedger(seq, *initialLoadObserver_);
+                        if (not res.has_value() and res.error() == InitialLedgerLoadError::Cancelled) {
+                            LOG(log_.debug()) << "Initial ledger load got cancelled";
+                            return std::nullopt;
+                        }
+
+                        ASSERT(res.has_value(), "Initial ledger retry logic failed");
+                        data.edgeKeys = std::move(res).value();
+
+                        return loader_->loadInitialLedger(data);
+                    }
+                );
+            });
+
+            if (not ledger.has_value()) {
+                LOG(log_.error()) << "Failed to load initial ledger. Exiting monitor loop";
+                return std::nullopt;
+            }
+
+            LOG(log_.debug()) << "Time to download and store ledger = " << timeDiff;
+            LOG(log_.info()) << "Finished loadInitialLedger. cache size = " << backend_->cache().size();
+
+            return backend_->hardFetchLedgerRangeNoThrow();
+        }
+
+        LOG(log_.info()) << "The wait for the next validated ledger has been aborted. "
+                            "Exiting monitor loop";
+        return std::nullopt;
+    }
+
+    LOG(log_.info()) << "Database already populated. Picking up from the tip of history";
+    cacheLoader_->load(rng->maxSequence);
+
+    return rng;
+}
+
+void
+ETLService::startMonitor(uint32_t seq)
+{
+    monitor_ = monitorProvider_->make(ctx_, backend_, ledgers_, seq);
+
+    monitorNewSeqSubscription_ = monitor_->subscribeToNewSequence([this](uint32_t seq) {
+        LOG(log_.info()) << "ETLService (via Monitor) got new seq from db: " << seq;
+
+        if (state_->writeConflict) {
+            LOG(log_.info()) << "Got a write conflict; Giving up writer seat immediately";
+            giveUpWriter();
+        }
+
+        if (not state_->isWriting) {
+            auto const diff = data::synchronousAndRetryOnTimeout([this, seq](auto yield) {
+                return backend_->fetchLedgerDiff(seq, yield);
+            });
+
+            cacheUpdater_->update(seq, diff);
+            backend_->updateRange(seq);
+        }
+
+        publisher_->publish(seq, {});
+    });
+
+    monitorDbStalledSubscription_ = monitor_->subscribeToDbStalled([this]() {
+        LOG(log_.warn()) << "ETLService received DbStalled signal from Monitor";
+        if (not state_->isStrictReadonly and not state_->isWriting)
+            attemptTakeoverWriter();
+    });
+
+    monitor_->run();
+}
+
+void
+ETLService::startLoading(uint32_t seq)
+{
+    ASSERT(not state_->isStrictReadonly, "This should only happen on writer nodes");
+    taskMan_ = taskManagerProvider_->make(ctx_, *monitor_, seq, finishSequence_);
+
+    // FIXME: this legacy name "extractor_threads" is no longer accurate (we have coroutines now)
+    taskMan_->run(config_.get().get<std::size_t>("extractor_threads"));
+}
+
+void
+ETLService::attemptTakeoverWriter()
+{
+    ASSERT(not state_->isStrictReadonly, "This should only happen on writer nodes");
+    auto rng = backend_->hardFetchLedgerRangeNoThrow();
+    ASSERT(rng.has_value(), "Ledger range can't be null");
+
+    state_->isWriting = true;  // switch to writer
+    LOG(log_.info()) << "Taking over the ETL writer seat";
+    startLoading(rng->maxSequence + 1);
+}
+
+void
+ETLService::giveUpWriter()
+{
+    ASSERT(not state_->isStrictReadonly, "This should only happen on writer nodes");
+    state_->isWriting = false;
+    state_->writeConflict = false;
+    taskMan_ = nullptr;
+}
+
+}  // namespace etlng
--- a/src/etlng/ETLService.hpp
+++ b/src/etlng/ETLService.hpp
@@ -0,0 +1,199 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2025, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "data/BackendInterface.hpp"
+#include "data/Types.hpp"
+#include "etl/ETLState.hpp"
+#include "etl/NetworkValidatedLedgersInterface.hpp"
+#include "etl/SystemState.hpp"
+#include "etl/impl/AmendmentBlockHandler.hpp"
+#include "etl/impl/LedgerFetcher.hpp"
+#include "etlng/CacheLoaderInterface.hpp"
+#include "etlng/CacheUpdaterInterface.hpp"
+#include "etlng/ETLServiceInterface.hpp"
+#include "etlng/ExtractorInterface.hpp"
+#include "etlng/InitialLoadObserverInterface.hpp"
+#include "etlng/LedgerPublisherInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
+#include "etlng/LoaderInterface.hpp"
+#include "etlng/MonitorInterface.hpp"
+#include "etlng/MonitorProviderInterface.hpp"
+#include "etlng/TaskManagerInterface.hpp"
+#include "etlng/TaskManagerProviderInterface.hpp"
+#include "etlng/impl/AmendmentBlockHandler.hpp"
+#include "etlng/impl/CacheUpdater.hpp"
+#include "etlng/impl/Extraction.hpp"
+#include "etlng/impl/LedgerPublisher.hpp"
+#include "etlng/impl/Loading.hpp"
+#include "etlng/impl/Registry.hpp"
+#include "etlng/impl/Scheduling.hpp"
+#include "etlng/impl/TaskManager.hpp"
+#include "etlng/impl/ext/Cache.hpp"
+#include "etlng/impl/ext/Core.hpp"
+#include "etlng/impl/ext/NFT.hpp"
+#include "etlng/impl/ext/Successor.hpp"
+#include "util/async/AnyExecutionContext.hpp"
+#include "util/async/AnyOperation.hpp"
+#include "util/config/ConfigDefinition.hpp"
+#include "util/log/Logger.hpp"
+
+#include <boost/asio/io_context.hpp>
+#include <boost/json/object.hpp>
+#include <boost/signals2/connection.hpp>
+#include <fmt/format.h>
+#include <xrpl/basics/Blob.h>
+#include <xrpl/basics/base_uint.h>
+#include <xrpl/basics/strHex.h>
+#include <xrpl/proto/org/xrpl/rpc/v1/get_ledger.pb.h>
+#include <xrpl/proto/org/xrpl/rpc/v1/ledger.pb.h>
+#include <xrpl/protocol/LedgerHeader.h>
+#include <xrpl/protocol/STTx.h>
+#include <xrpl/protocol/TxFormats.h>
+#include <xrpl/protocol/TxMeta.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <memory>
+#include <optional>
+#include <string>
+
+namespace etlng {
+
+/**
+ * @brief This class is responsible for continuously extracting data from a p2p node, and writing that data to the
+ * databases.
+ *
+ * Usually, multiple different processes share access to the same network accessible databases, in which case only one
+ * such process is performing ETL and writing to the database. The other processes simply monitor the database for new
+ * ledgers, and publish those ledgers to the various subscription streams. If a monitoring process determines that the
+ * ETL writer has failed (no new ledgers written for some time), the process will attempt to become the ETL writer.
+ *
+ * If there are multiple monitoring processes that try to become the ETL writer at the same time, one will win out, and
+ * the others will fall back to monitoring/publishing. In this sense, this class dynamically transitions from monitoring
+ * to writing and from writing to monitoring, based on the activity of other processes running on different machines.
+ */
+class ETLService : public ETLServiceInterface {
+    util::Logger log_{"ETL"};
+
+    util::async::AnyExecutionContext ctx_;
+    std::reference_wrapper<util::config::ClioConfigDefinition const> config_;
+    std::shared_ptr<BackendInterface> backend_;
+    std::shared_ptr<LoadBalancerInterface> balancer_;
+    std::shared_ptr<etl::NetworkValidatedLedgersInterface> ledgers_;
+    std::shared_ptr<LedgerPublisherInterface> publisher_;
+    std::shared_ptr<CacheLoaderInterface> cacheLoader_;
+    std::shared_ptr<CacheUpdaterInterface> cacheUpdater_;
+    std::shared_ptr<ExtractorInterface> extractor_;
+    std::shared_ptr<LoaderInterface> loader_;
+    std::shared_ptr<InitialLoadObserverInterface> initialLoadObserver_;
+    std::shared_ptr<etlng::TaskManagerProviderInterface> taskManagerProvider_;
+    std::shared_ptr<etlng::MonitorProviderInterface> monitorProvider_;
+    std::shared_ptr<etl::SystemState> state_;
+
+    std::optional<uint32_t> startSequence_;
+    std::optional<uint32_t> finishSequence_;
+
+    std::unique_ptr<MonitorInterface> monitor_;
+    std::unique_ptr<TaskManagerInterface> taskMan_;
+
+    boost::signals2::scoped_connection monitorNewSeqSubscription_;
+    boost::signals2::scoped_connection monitorDbStalledSubscription_;
+
+    std::optional<util::async::AnyOperation<void>> mainLoop_;
+
+public:
+    /**
+     * @brief Create an instance of ETLService.
+     *
+     * @param ctx The execution context for asynchronous operations
+     * @param config The Clio configuration definition
+     * @param backend Interface to the backend database
+     * @param balancer Load balancer for distributing work
+     * @param ledgers Interface for accessing network validated ledgers
+     * @param publisher Interface for publishing ledger data
+     * @param cacheLoader Interface for loading cache data
+     * @param cacheUpdater Interface for updating cache data
+     * @param extractor The extractor to use
+     * @param loader Interface for loading data
+     * @param initialLoadObserver The observer for initial data loading
+     * @param taskManagerProvider The provider of the task manager instance
+     * @param monitorProvider The provider of the monitor instance
+     * @param state System state tracking object
+     */
+    ETLService(
+        util::async::AnyExecutionContext ctx,
+        std::reference_wrapper<util::config::ClioConfigDefinition const> config,
+        std::shared_ptr<data::BackendInterface> backend,
+        std::shared_ptr<LoadBalancerInterface> balancer,
+        std::shared_ptr<etl::NetworkValidatedLedgersInterface> ledgers,
+        std::shared_ptr<LedgerPublisherInterface> publisher,
+        std::shared_ptr<CacheLoaderInterface> cacheLoader,
+        std::shared_ptr<CacheUpdaterInterface> cacheUpdater,
+        std::shared_ptr<ExtractorInterface> extractor,
+        std::shared_ptr<LoaderInterface> loader,
+        std::shared_ptr<InitialLoadObserverInterface> initialLoadObserver,
+        std::shared_ptr<etlng::TaskManagerProviderInterface> taskManagerProvider,
+        std::shared_ptr<etlng::MonitorProviderInterface> monitorProvider,
+        std::shared_ptr<etl::SystemState> state
+    );
+
+    ~ETLService() override;
+
+    void
+    run() override;
+
+    void
+    stop() override;
+
+    boost::json::object
+    getInfo() const override;
+
+    bool
+    isAmendmentBlocked() const override;
+
+    bool
+    isCorruptionDetected() const override;
+
+    std::optional<etl::ETLState>
+    getETLState() const override;
+
+    std::uint32_t
+    lastCloseAgeSeconds() const override;
+
+private:
+    std::optional<data::LedgerRange>
+    loadInitialLedgerIfNeeded();
+
+    void
+    startMonitor(uint32_t seq);
+
+    void
+    startLoading(uint32_t seq);
+
+    void
+    attemptTakeoverWriter();
+
+    void
+    giveUpWriter();
+};
+
+}  // namespace etlng
--- a/src/etlng/ETLServiceInterface.hpp
+++ b/src/etlng/ETLServiceInterface.hpp
@@ -26,7 +26,7 @@
 #include <cstdint>
 #include <optional>

-namespace etl {
+namespace etlng {

 /**
 * @brief This is a base class for any ETL service implementations.
@@ -77,7 +77,7 @@ struct ETLServiceInterface {
     * @brief Get the etl nodes' state
     * @return The etl nodes' state, nullopt if etl nodes are not connected
     */
-    [[nodiscard]] virtual std::optional<ETLState>
+    [[nodiscard]] virtual std::optional<etl::ETLState>
    getETLState() const = 0;

    /**
@@ -89,4 +89,4 @@ struct ETLServiceInterface {
    lastCloseAgeSeconds() const = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/ExtractorInterface.hpp
+++ b/src/etlng/ExtractorInterface.hpp
@@ -19,12 +19,12 @@

 #pragma once

-#include "etl/Models.hpp"
+#include "etlng/Models.hpp"

 #include <cstdint>
 #include <optional>

-namespace etl {
+namespace etlng {

 /**
 * @brief An interface for the Extractor
@@ -51,4 +51,4 @@ struct ExtractorInterface {
    extractLedgerOnly(uint32_t seq) = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/InitialLoadObserverInterface.hpp
+++ b/src/etlng/InitialLoadObserverInterface.hpp
@@ -19,7 +19,7 @@

 #pragma once

-#include "etl/Models.hpp"
+#include "etlng/Models.hpp"

 #include <xrpl/protocol/LedgerHeader.h>

@@ -28,7 +28,7 @@
 #include <string>
 #include <vector>

-namespace etl {
+namespace etlng {

 /**
 * @brief The interface for observing the initial ledger load
@@ -51,4 +51,4 @@ struct InitialLoadObserverInterface {
    ) = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/LedgerPublisherInterface.hpp
+++ b/src/etlng/LedgerPublisherInterface.hpp
@@ -23,7 +23,7 @@
 #include <cstdint>
 #include <optional>

-namespace etl {
+namespace etlng {

 /**
 * @brief The interface of a scheduler for the extraction process
@@ -71,4 +71,4 @@ struct LedgerPublisherInterface {
    lastPublishAgeSeconds() const = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/LoadBalancer.cpp
+++ b/src/etlng/LoadBalancer.cpp
@@ -0,0 +1,416 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "etlng/LoadBalancer.hpp"
+
+#include "data/BackendInterface.hpp"
+#include "etl/ETLState.hpp"
+#include "etl/NetworkValidatedLedgersInterface.hpp"
+#include "etlng/InitialLoadObserverInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
+#include "etlng/Source.hpp"
+#include "feed/SubscriptionManagerInterface.hpp"
+#include "rpc/Errors.hpp"
+#include "util/Assert.hpp"
+#include "util/CoroutineGroup.hpp"
+#include "util/Profiler.hpp"
+#include "util/Random.hpp"
+#include "util/ResponseExpirationCache.hpp"
+#include "util/config/ArrayView.hpp"
+#include "util/config/ConfigDefinition.hpp"
+#include "util/config/ObjectView.hpp"
+#include "util/log/Logger.hpp"
+#include "util/prometheus/Label.hpp"
+#include "util/prometheus/Prometheus.hpp"
+
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/spawn.hpp>
+#include <boost/json/array.hpp>
+#include <boost/json/object.hpp>
+#include <boost/json/value.hpp>
+#include <boost/json/value_to.hpp>
+#include <fmt/format.h>
+
+#include <algorithm>
+#include <chrono>
+#include <cstddef>
+#include <cstdint>
+#include <expected>
+#include <memory>
+#include <optional>
+#include <stdexcept>
+#include <string>
+#include <thread>
+#include <utility>
+#include <vector>
+
+using namespace util::config;
+using util::prometheus::Labels;
+
+namespace etlng {
+
+std::shared_ptr<LoadBalancerInterface>
+LoadBalancer::makeLoadBalancer(
+    ClioConfigDefinition const& config,
+    boost::asio::io_context& ioc,
+    std::shared_ptr<BackendInterface> backend,
+    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
+    std::unique_ptr<util::RandomGeneratorInterface> randomGenerator,
+    std::shared_ptr<etl::NetworkValidatedLedgersInterface> validatedLedgers,
+    SourceFactory sourceFactory
+)
+{
+    return std::make_shared<LoadBalancer>(
+        config,
+        ioc,
+        std::move(backend),
+        std::move(subscriptions),
+        std::move(randomGenerator),
+        std::move(validatedLedgers),
+        std::move(sourceFactory)
+    );
+}
+
+LoadBalancer::LoadBalancer(
+    ClioConfigDefinition const& config,
+    boost::asio::io_context& ioc,
+    std::shared_ptr<BackendInterface> backend,
+    std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
+    std::unique_ptr<util::RandomGeneratorInterface> randomGenerator,
+    std::shared_ptr<etl::NetworkValidatedLedgersInterface> validatedLedgers,
+    SourceFactory sourceFactory
+)
+    : randomGenerator_(std::move(randomGenerator))
+    , forwardingCounters_{
+          .successDuration = PrometheusService::counterInt(
+              "forwarding_duration_milliseconds_counter",
+              Labels({util::prometheus::Label{"status", "success"}}),
+              "The duration of processing successful forwarded requests"
+          ),
+          .failDuration = PrometheusService::counterInt(
+              "forwarding_duration_milliseconds_counter",
+              Labels({util::prometheus::Label{"status", "fail"}}),
+              "The duration of processing failed forwarded requests"
+          ),
+          .retries = PrometheusService::counterInt(
+              "forwarding_retries_counter",
+              Labels(),
+              "The number of retries before a forwarded request was successful. Initial attempt excluded"
+          ),
+          .cacheHit = PrometheusService::counterInt(
+              "forwarding_cache_hit_counter",
+              Labels(),
+              "The number of requests that we served from the cache"
+          ),
+          .cacheMiss = PrometheusService::counterInt(
+              "forwarding_cache_miss_counter",
+              Labels(),
+              "The number of requests that were not served from the cache"
+          )
+      }
+{
+    auto const forwardingCacheTimeout = config.get<float>("forwarding.cache_timeout");
+    if (forwardingCacheTimeout > 0.f) {
+        forwardingCache_ = util::ResponseExpirationCache{
+            util::config::ClioConfigDefinition::toMilliseconds(forwardingCacheTimeout),
+            {"server_info", "server_state", "server_definitions", "fee", "ledger_closed"}
+        };
+    }
+
+    auto const numMarkers = config.getValueView("num_markers");
+    if (numMarkers.hasValue()) {
+        auto const value = numMarkers.asIntType<uint32_t>();
+        downloadRanges_ = value;
+    } else if (backend->fetchLedgerRange()) {
+        downloadRanges_ = 4;
+    }
+
+    auto const allowNoEtl = config.get<bool>("allow_no_etl");
+
+    auto const checkOnETLFailure = [this, allowNoEtl](std::string const& log) {
+        LOG(log_.warn()) << log;
+
+        if (!allowNoEtl) {
+            LOG(log_.error()) << "Set allow_no_etl as true in config to allow clio run without valid ETL sources.";
+            throw std::logic_error("ETL configuration error.");
+        }
+    };
+
+    auto const forwardingTimeout =
+        ClioConfigDefinition::toMilliseconds(config.get<float>("forwarding.request_timeout"));
+    auto const etlArray = config.getArray("etl_sources");
+    for (auto it = etlArray.begin<ObjectView>(); it != etlArray.end<ObjectView>(); ++it) {
+        auto source = sourceFactory(
+            *it,
+            ioc,
+            subscriptions,
+            validatedLedgers,
+            forwardingTimeout,
+            [this]() {
+                if (not hasForwardingSource_.lock().get())
+                    chooseForwardingSource();
+            },
+            [this](bool wasForwarding) {
+                if (wasForwarding)
+                    chooseForwardingSource();
+            },
+            [this]() {
+                if (forwardingCache_.has_value())
+                    forwardingCache_->invalidate();
+            }
+        );
+
+        // checking etl node validity
+        auto const stateOpt = etl::ETLState::fetchETLStateFromSource(*source);
+
+        if (!stateOpt) {
+            LOG(log_.warn()) << "Failed to fetch ETL state from source = " << source->toString()
+                             << " Please check the configuration and network";
+        } else if (etlState_ && etlState_->networkID != stateOpt->networkID) {
+            checkOnETLFailure(
+                fmt::format(
+                    "ETL sources must be on the same network. Source network id = {} does not match others network id "
+                    "= {}",
+                    stateOpt->networkID,
+                    etlState_->networkID
+                )
+            );
+        } else {
+            etlState_ = stateOpt;
+        }
+
+        sources_.push_back(std::move(source));
+        LOG(log_.info()) << "Added etl source - " << sources_.back()->toString();
+    }
+
+    if (!etlState_)
+        checkOnETLFailure("Failed to fetch ETL state from any source. Please check the configuration and network");
+
+    if (sources_.empty())
+        checkOnETLFailure("No ETL sources configured. Please check the configuration");
+
+    // This is made separate from source creation to prevent UB in case one of the sources will call
+    // chooseForwardingSource while we are still filling the sources_ vector
+    for (auto const& source : sources_) {
+        source->run();
+    }
+}
+
+InitialLedgerLoadResult
+LoadBalancer::loadInitialLedger(
+    uint32_t sequence,
+    etlng::InitialLoadObserverInterface& loadObserver,
+    std::chrono::steady_clock::duration retryAfter
+)
+{
+    InitialLedgerLoadResult response;
+
+    execute(
+        [this, &response, &sequence, &loadObserver](auto& source) {
+            auto res = source->loadInitialLedger(sequence, downloadRanges_, loadObserver);
+
+            if (not res.has_value() and res.error() == InitialLedgerLoadError::Errored) {
+                LOG(log_.error()) << "Failed to download initial ledger."
+                                  << " Sequence = " << sequence << " source = " << source->toString();
+                return false;  // should retry on error
+            }
+
+            response = std::move(res);  // cancelled or data received
+            return true;
+        },
+        sequence,
+        retryAfter
+    );
+
+    return response;
+}
+
+LoadBalancer::OptionalGetLedgerResponseType
+LoadBalancer::fetchLedger(
+    uint32_t ledgerSequence,
+    bool getObjects,
+    bool getObjectNeighbors,
+    std::chrono::steady_clock::duration retryAfter
+)
+{
+    GetLedgerResponseType response;
+    execute(
+        [&response, ledgerSequence, getObjects, getObjectNeighbors, log = log_](auto& source) {
+            auto [status, data] = source->fetchLedger(ledgerSequence, getObjects, getObjectNeighbors);
+            response = std::move(data);
+            if (status.ok() && response.validated()) {
+                LOG(log.info()) << "Successfully fetched ledger = " << ledgerSequence
+                                << " from source = " << source->toString();
+                return true;
+            }
+
+            LOG(log.warn()) << "Could not fetch ledger " << ledgerSequence << ", Reply: " << response.DebugString()
+                            << ", error_code: " << status.error_code() << ", error_msg: " << status.error_message()
+                            << ", source = " << source->toString();
+            return false;
+        },
+        ledgerSequence,
+        retryAfter
+    );
+    return response;
+}
+
+std::expected<boost::json::object, rpc::CombinedError>
+LoadBalancer::forwardToRippled(
+    boost::json::object const& request,
+    std::optional<std::string> const& clientIp,
+    bool isAdmin,
+    boost::asio::yield_context yield
+)
+{
+    if (not request.contains("command"))
+        return std::unexpected{rpc::ClioError::RpcCommandIsMissing};
+
+    auto const cmd = boost::json::value_to<std::string>(request.at("command"));
+    if (forwardingCache_) {
+        if (auto cachedResponse = forwardingCache_->get(cmd); cachedResponse) {
+            forwardingCounters_.cacheHit.get() += 1;
+            return std::move(cachedResponse).value();
+        }
+    }
+    forwardingCounters_.cacheMiss.get() += 1;
+
+    ASSERT(not sources_.empty(), "ETL sources must be configured to forward requests.");
+    std::size_t sourceIdx = randomGenerator_->uniform(0ul, sources_.size() - 1);
+
+    auto numAttempts = 0u;
+
+    auto xUserValue = isAdmin ? kADMIN_FORWARDING_X_USER_VALUE : kUSER_FORWARDING_X_USER_VALUE;
+
+    std::optional<boost::json::object> response;
+    rpc::ClioError error = rpc::ClioError::EtlConnectionError;
+    while (numAttempts < sources_.size()) {
+        auto [res, duration] =
+            util::timed([&]() { return sources_[sourceIdx]->forwardToRippled(request, clientIp, xUserValue, yield); });
+        if (res) {
+            forwardingCounters_.successDuration.get() += duration;
+            response = std::move(res).value();
+            break;
+        }
+        forwardingCounters_.failDuration.get() += duration;
+        ++forwardingCounters_.retries.get();
+        error = std::max(error, res.error());  // Choose the best result between all sources
+
+        sourceIdx = (sourceIdx + 1) % sources_.size();
+        ++numAttempts;
+    }
+
+    if (response) {
+        if (forwardingCache_ and not response->contains("error"))
+            forwardingCache_->put(cmd, *response);
+        return std::move(response).value();
+    }
+
+    return std::unexpected{error};
+}
+
+boost::json::value
+LoadBalancer::toJson() const
+{
+    boost::json::array ret;
+    for (auto& src : sources_)
+        ret.push_back(src->toJson());
+
+    return ret;
+}
+
+template <typename Func>
+void
+LoadBalancer::execute(Func f, uint32_t ledgerSequence, std::chrono::steady_clock::duration retryAfter)
+{
+    ASSERT(not sources_.empty(), "ETL sources must be configured to execute functions.");
+    size_t sourceIdx = randomGenerator_->uniform(0ul, sources_.size() - 1);
+
+    size_t numAttempts = 0;
+
+    while (true) {
+        auto& source = sources_[sourceIdx];
+
+        LOG(log_.debug()) << "Attempting to execute func. ledger sequence = " << ledgerSequence
+                          << " - source = " << source->toString();
+        // Originally, it was (source->hasLedger(ledgerSequence) || true)
+        /* Sometimes rippled has ledger but doesn't actually know. However,
+        but this does NOT happen in the normal case and is safe to remove
+        This || true is only needed when loading full history standalone */
+        if (source->hasLedger(ledgerSequence)) {
+            bool const res = f(source);
+            if (res) {
+                LOG(log_.debug()) << "Successfully executed func at source = " << source->toString()
+                                  << " - ledger sequence = " << ledgerSequence;
+                break;
+            }
+
+            LOG(log_.warn()) << "Failed to execute func at source = " << source->toString()
+                             << " - ledger sequence = " << ledgerSequence;
+        } else {
+            LOG(log_.warn()) << "Ledger not present at source = " << source->toString()
+                             << " - ledger sequence = " << ledgerSequence;
+        }
+        sourceIdx = (sourceIdx + 1) % sources_.size();
+        numAttempts++;
+        if (numAttempts % sources_.size() == 0) {
+            LOG(log_.info()) << "Ledger sequence " << ledgerSequence
+                             << " is not yet available from any configured sources. Sleeping and trying again";
+            std::this_thread::sleep_for(retryAfter);
+        }
+    }
+}
+
+std::optional<etl::ETLState>
+LoadBalancer::getETLState() noexcept
+{
+    if (!etlState_) {
+        // retry ETLState fetch
+        etlState_ = etl::ETLState::fetchETLStateFromSource(*this);
+    }
+    return etlState_;
+}
+
+void
+LoadBalancer::stop(boost::asio::yield_context yield)
+{
+    util::CoroutineGroup group{yield};
+    std::ranges::for_each(sources_, [&group, yield](auto& source) {
+        group.spawn(yield, [&source](boost::asio::yield_context innerYield) { source->stop(innerYield); });
+    });
+    group.asyncWait(yield);
+}
+
+void
+LoadBalancer::chooseForwardingSource()
+{
+    LOG(log_.info()) << "Choosing a new source to forward subscriptions";
+    auto hasForwardingSourceLock = hasForwardingSource_.lock();
+    hasForwardingSourceLock.get() = false;
+    for (auto& source : sources_) {
+        if (not hasForwardingSourceLock.get() and source->isConnected()) {
+            source->setForwarding(true);
+            hasForwardingSourceLock.get() = true;
+        } else {
+            source->setForwarding(false);
+        }
+    }
+}
+
+}  // namespace etlng
--- a/src/etlng/LoadBalancer.hpp
+++ b/src/etlng/LoadBalancer.hpp
@@ -0,0 +1,287 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2022, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include "data/BackendInterface.hpp"
+#include "etl/ETLState.hpp"
+#include "etl/NetworkValidatedLedgersInterface.hpp"
+#include "etlng/InitialLoadObserverInterface.hpp"
+#include "etlng/LoadBalancerInterface.hpp"
+#include "etlng/Source.hpp"
+#include "feed/SubscriptionManagerInterface.hpp"
+#include "rpc/Errors.hpp"
+#include "util/Assert.hpp"
+#include "util/Mutex.hpp"
+#include "util/Random.hpp"
+#include "util/ResponseExpirationCache.hpp"
+#include "util/config/ConfigDefinition.hpp"
+#include "util/log/Logger.hpp"
+#include "util/prometheus/Counter.hpp"
+
+#include <boost/asio.hpp>
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/spawn.hpp>
+#include <boost/json/object.hpp>
+#include <boost/json/value.hpp>
+#include <grpcpp/grpcpp.h>
+#include <org/xrpl/rpc/v1/get_ledger.pb.h>
+#include <org/xrpl/rpc/v1/ledger.pb.h>
+#include <xrpl/proto/org/xrpl/rpc/v1/xrp_ledger.grpc.pb.h>
+
+#include <chrono>
+#include <concepts>
+#include <cstdint>
+#include <expected>
+#include <functional>
+#include <memory>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+namespace etlng {
+
+/**
+ * @brief A tag class to help identify LoadBalancer in templated code.
+ */
+struct LoadBalancerTag {
+    virtual ~LoadBalancerTag() = default;
+};
+
+template <typename T>
+concept SomeLoadBalancer = std::derived_from<T, LoadBalancerTag>;
+
+/**
+ * @brief This class is used to manage connections to transaction processing processes.
+ *
+ * This class spawns a listener for each etl source, which listens to messages on the ledgers stream (to keep track of
+ * which ledgers have been validated by the network, and the range of ledgers each etl source has). This class also
+ * allows requests for ledger data to be load balanced across all possible ETL sources.
+ */
+class LoadBalancer : public etlng::LoadBalancerInterface, LoadBalancerTag {
+public:
+    using RawLedgerObjectType = org::xrpl::rpc::v1::RawLedgerObject;
+    using GetLedgerResponseType = org::xrpl::rpc::v1::GetLedgerResponse;
+    using OptionalGetLedgerResponseType = std::optional<GetLedgerResponseType>;
+
+private:
+    static constexpr std::uint32_t kDEFAULT_DOWNLOAD_RANGES = 16;
+
+    util::Logger log_{"ETL"};
+    // Forwarding cache must be destroyed after sources because sources have a callback to invalidate cache
+    std::optional<util::ResponseExpirationCache> forwardingCache_;
+    std::optional<std::string> forwardingXUserValue_;
+
+    std::unique_ptr<util::RandomGeneratorInterface> randomGenerator_;
+
+    std::vector<SourcePtr> sources_;
+    std::optional<etl::ETLState> etlState_;
+    std::uint32_t downloadRanges_ =
+        kDEFAULT_DOWNLOAD_RANGES; /*< The number of markers to use when downloading initial ledger */
+
+    struct ForwardingCounters {
+        std::reference_wrapper<util::prometheus::CounterInt> successDuration;
+        std::reference_wrapper<util::prometheus::CounterInt> failDuration;
+        std::reference_wrapper<util::prometheus::CounterInt> retries;
+        std::reference_wrapper<util::prometheus::CounterInt> cacheHit;
+        std::reference_wrapper<util::prometheus::CounterInt> cacheMiss;
+    } forwardingCounters_;
+
+    // Using mutext instead of atomic_bool because choosing a new source to
+    // forward messages should be done with a mutual exclusion otherwise there will be a race condition
+    util::Mutex<bool> hasForwardingSource_{false};
+
+public:
+    /**
+     * @brief Value for the X-User header when forwarding admin requests
+     */
+    static constexpr std::string_view kADMIN_FORWARDING_X_USER_VALUE = "clio_admin";
+
+    /**
+     * @brief Value for the X-User header when forwarding user requests
+     */
+    static constexpr std::string_view kUSER_FORWARDING_X_USER_VALUE = "clio_user";
+
+    /**
+     * @brief Create an instance of the load balancer.
+     *
+     * @param config The configuration to use
+     * @param ioc The io_context to run on
+     * @param backend BackendInterface implementation
+     * @param subscriptions Subscription manager
+     * @param randomGenerator A random generator to use for selecting sources
+     * @param validatedLedgers The network validated ledgers datastructure
+     * @param sourceFactory A factory function to create a source
+     */
+    LoadBalancer(
+        util::config::ClioConfigDefinition const& config,
+        boost::asio::io_context& ioc,
+        std::shared_ptr<BackendInterface> backend,
+        std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
+        std::unique_ptr<util::RandomGeneratorInterface> randomGenerator,
+        std::shared_ptr<etl::NetworkValidatedLedgersInterface> validatedLedgers,
+        SourceFactory sourceFactory = makeSource
+    );
+
+    /**
+     * @brief A factory function for the load balancer.
+     *
+     * @param config The configuration to use
+     * @param ioc The io_context to run on
+     * @param backend BackendInterface implementation
+     * @param subscriptions Subscription manager
+     * @param randomGenerator A random generator to use for selecting sources
+     * @param validatedLedgers The network validated ledgers datastructure
+     * @param sourceFactory A factory function to create a source
+     * @return A shared pointer to a new instance of LoadBalancer
+     */
+    static std::shared_ptr<LoadBalancerInterface>
+    makeLoadBalancer(
+        util::config::ClioConfigDefinition const& config,
+        boost::asio::io_context& ioc,
+        std::shared_ptr<BackendInterface> backend,
+        std::shared_ptr<feed::SubscriptionManagerInterface> subscriptions,
+        std::unique_ptr<util::RandomGeneratorInterface> randomGenerator,
+        std::shared_ptr<etl::NetworkValidatedLedgersInterface> validatedLedgers,
+        SourceFactory sourceFactory = makeSource
+    );
+
+    /**
+     * @brief Load the initial ledger, writing data to the queue.
+     * @note This function will retry indefinitely until the ledger is downloaded.
+     *
+     * @param sequence Sequence of ledger to download
+     * @param retryAfter Time to wait between retries (2 seconds by default)
+     * @return A std::vector<std::string> The ledger data
+     */
+    std::vector<std::string>
+    loadInitialLedger(
+        [[maybe_unused]] uint32_t sequence,
+        [[maybe_unused]] std::chrono::steady_clock::duration retryAfter
+    ) override
+    {
+        ASSERT(false, "Not available for new ETL");
+        std::unreachable();
+    };
+
+    /**
+     * @brief Load the initial ledger, writing data to the queue.
+     * @note This function will retry indefinitely until the ledger is downloaded or the download is cancelled.
+     *
+     * @param sequence Sequence of ledger to download
+     * @param observer The observer to notify of progress
+     * @param retryAfter Time to wait between retries (2 seconds by default)
+     * @return A std::expected with ledger edge keys on success, or InitialLedgerLoadError on failure
+     */
+    InitialLedgerLoadResult
+    loadInitialLedger(
+        uint32_t sequence,
+        etlng::InitialLoadObserverInterface& observer,
+        std::chrono::steady_clock::duration retryAfter
+    ) override;
+
+    /**
+     * @brief Fetch data for a specific ledger.
+     *
+     * This function will continuously try to fetch data for the specified ledger until the fetch succeeds, the ledger
+     * is found in the database, or the server is shutting down.
+     *
+     * @param ledgerSequence Sequence of the ledger to fetch
+     * @param getObjects Whether to get the account state diff between this ledger and the prior one
+     * @param getObjectNeighbors Whether to request object neighbors
+     * @param retryAfter Time to wait between retries (2 seconds by default)
+     * @return The extracted data, if extraction was successful. If the ledger was found
+     * in the database or the server is shutting down, the optional will be empty
+     */
+    OptionalGetLedgerResponseType
+    fetchLedger(
+        uint32_t ledgerSequence,
+        bool getObjects,
+        bool getObjectNeighbors,
+        std::chrono::steady_clock::duration retryAfter = std::chrono::seconds{2}
+    ) override;
+
+    /**
+     * @brief Represent the state of this load balancer as a JSON object
+     *
+     * @return JSON representation of the state of this load balancer.
+     */
+    boost::json::value
+    toJson() const override;
+
+    /**
+     * @brief Forward a JSON RPC request to a randomly selected rippled node.
+     *
+     * @param request JSON-RPC request to forward
+     * @param clientIp The IP address of the peer, if known
+     * @param isAdmin Whether the request is from an admin
+     * @param yield The coroutine context
+     * @return Response received from rippled node as JSON object on success or error on failure
+     */
+    std::expected<boost::json::object, rpc::CombinedError>
+    forwardToRippled(
+        boost::json::object const& request,
+        std::optional<std::string> const& clientIp,
+        bool isAdmin,
+        boost::asio::yield_context yield
+    ) override;
+
+    /**
+     * @brief Return state of ETL nodes.
+     * @return ETL state, nullopt if etl nodes not available
+     */
+    std::optional<etl::ETLState>
+    getETLState() noexcept override;
+
+    /**
+     * @brief Stop the load balancer. This will stop all subscription sources.
+     * @note This function will asynchronously wait for all sources to stop.
+     *
+     * @param yield The coroutine context
+     */
+    void
+    stop(boost::asio::yield_context yield) override;
+
+private:
+    /**
+     * @brief Execute a function on a randomly selected source.
+     *
+     * @note f is a function that takes an Source as an argument and returns a bool.
+     * Attempt to execute f for one randomly chosen Source that has the specified ledger. If f returns false, another
+     * randomly chosen Source is used. The process repeats until f returns true.
+     *
+     * @param f Function to execute. This function takes the ETL source as an argument, and returns a bool
+     * @param ledgerSequence f is executed for each Source that has this ledger
+     * @param retryAfter Time to wait between retries (2 seconds by default)
+     * server is shutting down
+     */
+    template <typename Func>
+    void
+    execute(Func f, uint32_t ledgerSequence, std::chrono::steady_clock::duration retryAfter = std::chrono::seconds{2});
+
+    /**
+     * @brief Choose a new source to forward requests
+     */
+    void
+    chooseForwardingSource();
+};
+
+}  // namespace etlng
--- a/src/etlng/LoadBalancerInterface.hpp
+++ b/src/etlng/LoadBalancerInterface.hpp
@@ -21,7 +21,7 @@
 #pragma once

 #include "etl/ETLState.hpp"
-#include "etl/InitialLoadObserverInterface.hpp"
+#include "etlng/InitialLoadObserverInterface.hpp"
 #include "rpc/Errors.hpp"

 #include <boost/asio/spawn.hpp>
@@ -37,7 +37,7 @@
 #include <string>
 #include <vector>

-namespace etl {
+namespace etlng {

 /**
 * @brief Represents possible errors for initial ledger load
@@ -76,10 +76,21 @@ public:
    [[nodiscard]] virtual InitialLedgerLoadResult
    loadInitialLedger(
        uint32_t sequence,
-        InitialLoadObserverInterface& loader,
+        etlng::InitialLoadObserverInterface& loader,
        std::chrono::steady_clock::duration retryAfter = std::chrono::seconds{2}
    ) = 0;

+    /**
+     * @brief Load the initial ledger, writing data to the queue.
+     * @note This function will retry indefinitely until the ledger is downloaded.
+     *
+     * @param sequence Sequence of ledger to download
+     * @param retryAfter Time to wait between retries (2 seconds by default)
+     * @return A std::vector<std::string> The ledger data
+     */
+    [[nodiscard]] virtual std::vector<std::string>
+    loadInitialLedger(uint32_t sequence, std::chrono::steady_clock::duration retryAfter = std::chrono::seconds{2}) = 0;
+
    /**
     * @brief Fetch data for a specific ledger.
     *
@@ -130,7 +141,7 @@ public:
     * @brief Return state of ETL nodes.
     * @return ETL state, nullopt if etl nodes not available
     */
-    [[nodiscard]] virtual std::optional<ETLState>
+    [[nodiscard]] virtual std::optional<etl::ETLState>
    getETLState() noexcept = 0;

    /**
@@ -143,4 +154,4 @@ public:
    stop(boost::asio::yield_context yield) = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/LoaderInterface.hpp
+++ b/src/etlng/LoaderInterface.hpp
@@ -19,14 +19,14 @@

 #pragma once

-#include "etl/Models.hpp"
+#include "etlng/Models.hpp"

 #include <xrpl/protocol/LedgerHeader.h>

 #include <expected>
 #include <optional>

-namespace etl {
+namespace etlng {

 /**
 * @brief Enumeration of possible errors that can occur during loading operations
@@ -59,4 +59,4 @@ struct LoaderInterface {
    loadInitialLedger(model::LedgerData const& data) = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/Models.hpp
+++ b/src/etlng/Models.hpp
@@ -38,7 +38,7 @@
 #include <string>
 #include <vector>

-namespace etl::model {
+namespace etlng::model {

 /**
 * @brief A specification for the Registry.
@@ -190,4 +190,4 @@ struct Task {
    uint32_t seq;
 };

-}  // namespace etl::model
+}  // namespace etlng::model
--- a/src/etlng/MonitorInterface.hpp
+++ b/src/etlng/MonitorInterface.hpp
@@ -26,7 +26,7 @@
 #include <chrono>
 #include <cstdint>

-namespace etl {
+namespace etlng {

 /**
 * @brief An interface for the monitor service
@@ -88,4 +88,4 @@ public:
    stop() = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/src/etlng/MonitorProviderInterface.hpp
+++ b/src/etlng/MonitorProviderInterface.hpp
@@ -20,15 +20,15 @@
 #pragma once

 #include "data/BackendInterface.hpp"
-#include "etl/MonitorInterface.hpp"
 #include "etl/NetworkValidatedLedgersInterface.hpp"
+#include "etlng/MonitorInterface.hpp"
 #include "util/async/AnyExecutionContext.hpp"

 #include <chrono>
 #include <cstdint>
 #include <memory>

-namespace etl {
+namespace etlng {

 /**
 * @brief An interface for providing Monitor instances
@@ -55,10 +55,10 @@ struct MonitorProviderInterface {
    make(
        util::async::AnyExecutionContext ctx,
        std::shared_ptr<BackendInterface> backend,
-        std::shared_ptr<NetworkValidatedLedgersInterface> validatedLedgers,
+        std::shared_ptr<etl::NetworkValidatedLedgersInterface> validatedLedgers,
        uint32_t startSequence,
        std::chrono::steady_clock::duration dbStalledReportDelay = kDEFAULT_DB_STALLED_REPORT_DELAY
    ) = 0;
 };

-}  // namespace etl
+}  // namespace etlng
--- a/Show More
+++ b/Show More