Improve AccountID base58 conversion cache:

The previous cache guarded a configurably-sized vector with 64
packed spinlocks. Two aspects of that setup were not worth the
cost:

- Callers were forced to perform atomic RMW operations on a
  single word which was shared by all 64 locks; this caused
  the lock line to bounce between cores on every lookup.

- The configurable size and runtime initialization resulted
  in complexity that did not yield a meaningful improvement
  in performance.

This commit ditches the 64 packed spinlocks, replacing them
with per-entry sequence locks, allowing readers on the fast
path to avoid performing any stores at all.

Cache entries are now carefully sized and aligned to fit into
a typical cache line, which helps avoid false sharing and any
unnecessary coherence traffic.

The cache is now a fixed array of 65,536 entries. The size was
chosen to balance capacity against memory overhead and to keep
the indexing operation fast and simple: since AccountID values
are uniformly distributed, two bytes can serve directly as the
index without requiring additional hashing.

Note: The reader path will perform unsynchronized reads against
      concurrent writes; the sequence lock protocol detects and
      discards any data observed mid-update, so these races are
      benign. A sanitizer like TSAN can still flag them and the
      warnings are expected. A compile-time knob to disable the
      cache is available, if necessary.

include/xrpl/basics/CountedObject.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <xrpl/beast/type_name.h>
+#include <boost/core/type_name.hpp>
 
 #include <atomic>
 #include <string>
@@ -112,7 +112,7 @@ private:
     static auto&
     getCounter() noexcept
     {
-        static CountedObjects::Counter kC{beast::typeName<Object>()};
+        static CountedObjects::Counter kC{boost::core::type_name<Object>()};
         return kC;
     }
 

include/xrpl/basics/SlabAllocator.h

@@ -3,11 +3,11 @@
 #pragma once
 
 #include <xrpl/basics/ByteUtilities.h>
-#include <xrpl/beast/type_name.h>
 #include <xrpl/beast/utility/instrumentation.h>
 
 #include <boost/align.hpp>
 #include <boost/container/static_vector.hpp>
+#include <boost/core/type_name.hpp>
 #include <boost/predef.h>
 
 #include <algorithm>
@@ -16,6 +16,7 @@
 #include <cstring>
 #include <mutex>
 #include <stdexcept>
+#include <typeinfo>
 #include <vector>
 
 #if BOOST_OS_LINUX
@@ -335,7 +336,7 @@ public:
                 }) != cfg.end())
         {
             throw std::runtime_error(
-                "SlabAllocatorSet<" + beast::typeName<Type>() + ">: duplicate slab size");
+                "SlabAllocatorSet<" + boost::core::type_name<Type>() + ">: duplicate slab size");
         }
 
         for (auto const& c : cfg)

include/xrpl/basics/contract.h

@@ -1,7 +1,8 @@
 #pragma once
 
 #include <xrpl/basics/sanitizers.h>
-#include <xrpl/beast/type_name.h>
+
+#include <boost/core/type_name.hpp>
 
 #include <exception>
 #include <string>
@@ -55,7 +56,7 @@ Throw(Args&&... args)
         std::is_convertible_v<E*, std::exception*>, "Exception must derive from std::exception.");
 
     E e(std::forward<Args>(args)...);
-    logThrow(std::string("Throwing exception of type " + beast::typeName<E>() + ": ") + e.what());
+    logThrow("Throwing exception of type " + boost::core::type_name<E>() + ": " + e.what());
     throw std::move(e);
 }
 

include/xrpl/basics/safe_cast.h

@@ -2,107 +2,212 @@
 
 #include <xrpl/beast/utility/instrumentation.h>  // IWYU pragma: keep
 
+#include <concepts>
+#include <cstdint>
+#include <limits>
+#include <memory>
 #include <type_traits>
+#include <utility>
 
 namespace xrpl {
 
-// safe_cast adds compile-time checks to a static_cast to ensure that
-// the destination can hold all values of the source.  This is particularly
-// handy when the source or destination is an enumeration type.
+/** Every value of @p Src can be represented by @p Dest.
 
-template <class Src, class Dest>
-concept SafeToCast = (std::is_integral_v<Src> && std::is_integral_v<Dest>) &&
-    (std::is_signed_v<Src> || std::is_unsigned_v<Dest>) &&
-    (std::is_signed_v<Src> != std::is_signed_v<Dest> ? sizeof(Dest) > sizeof(Src)
-                                                     : sizeof(Dest) >= sizeof(Src));
+    Given two integral types, the cast is safe when the destination can
+    hold every possible value of the source.
 
-template <class Dest, class Src>
+    Comparing the bounds requires care: we use @c std::cmp_less_equal and
+    @c std::cmp_greater_equal; the plain relational operators would apply
+    arithmetic conversions, resulting in incorrect results when comparing
+    across signedness.
+
+    Because @c std::cmp_* requires standard signed or unsigned integer
+    arguments, which excludes character types and bool, we first widen
+    all type bounds to the maximum-width integer type while preserving
+    signedness.
+
+    @note Extended integer types, like __int128 on gcc, cannot be safely
+          widened to a standard integer type, so the concept will reject
+          them.
+*/
+template <typename Src, typename Dest>
+concept SafeToCast = std::is_integral_v<Src> && std::is_integral_v<Dest> && []() consteval {
+    using WideSrc = std::conditional_t<std::is_signed_v<Src>, std::intmax_t, std::uintmax_t>;
+    using WideDest = std::conditional_t<std::is_signed_v<Dest>, std::intmax_t, std::uintmax_t>;
+
+    // Note: this guard must be an evaluated branch, and not a
+    // static_assert. The lambda body is outside the immediate
+    // context, so a substitution-time failure here would be a
+    // hard error rather than leaving the concept unsatisfied.
+    if constexpr (sizeof(Src) > sizeof(WideSrc) || sizeof(Dest) > sizeof(WideDest))
+    {
+        return false;
+    }
+    else
+    {
+        return std::cmp_less_equal(
+                   static_cast<WideDest>(std::numeric_limits<Dest>::min()),
+                   static_cast<WideSrc>(std::numeric_limits<Src>::min())) &&
+            std::cmp_greater_equal(
+                   static_cast<WideDest>(std::numeric_limits<Dest>::max()),
+                   static_cast<WideSrc>(std::numeric_limits<Src>::max()));
+    }
+}();
+
+/** Compile-time-checked static_cast that rejects non-value preserving casts.
+
+    @note There is deliberately no enum-to-enum overload, and no overload
+          returning the underlying type of an enum. For the latter, use
+          @c std::to_underlying.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 {
     static_assert(
-        std::is_signed_v<Dest> || std::is_unsigned_v<Src>, "Cannot cast signed to unsigned");
-    constexpr unsigned kNotSame = std::is_signed_v<Dest> != std::is_signed_v<Src>;
-    static_assert(
-        sizeof(Dest) >= sizeof(Src) + kNotSame,
-        "Destination is too small to hold all values of source");
+        SafeToCast<Src, Dest>, "This cast is not value-preserving. Please use unsafeCast instead.");
     return static_cast<Dest>(s);
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 {
     return static_cast<Dest>(safeCast<std::underlying_type_t<Dest>>(s));
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 constexpr Dest
 safeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 {
-    return safeCast<Dest>(static_cast<std::underlying_type_t<Src>>(s));
+    return safeCast<Dest>(std::to_underlying(s));
 }
+/** @} */
 
-// unsafe_cast explicitly flags a static_cast as not necessarily able to hold
-// all values of the source. It includes a compile-time check so that if
-// underlying types become safe, it can be converted to a safe_cast.
+/** Integral-to-integral cast that is known to be narrowing or sign-erasing.
 
-template <class Dest, class Src>
+    This explicitly flags a conversion that can lose information for some
+    values of the source type, where the call site accepts that loss (or
+    truncation is the intended behavior).
+
+    The compile-time check ensures the cast remains "unsafe": if the types
+    involved later change such that the conversion becomes inherently
+    value-preserving, the static assertion fires with instructions to
+    migrate the call site to @ref safeCast.
+
+    If the conversion's safety depends on a runtime precondition rather
+    than on the types, or varies across instantiations of generic code,
+    use @ref checkedCast instead.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
 {
     static_assert(
-        !SafeToCast<Src, Dest>,
-        "Only unsafe if casting signed to unsigned or "
-        "destination is too small");
+        !SafeToCast<Src, Dest>, "This cast is value-preserving. Please use safeCast instead.");
     return static_cast<Dest>(s);
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
 {
     return static_cast<Dest>(unsafeCast<std::underlying_type_t<Dest>>(s));
 }
 
-template <class Dest, class Src>
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 constexpr Dest
 unsafeCast(Src s) noexcept
-    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
 {
-    return unsafeCast<Dest>(static_cast<std::underlying_type_t<Src>>(s));
+    return unsafeCast<Dest>(std::to_underlying(s));
+}
+/** @} */
+
+/** Integral-to-integral cast when the caller has performed a bounds check.
+
+    This documents that a runtime precondition or external invariant, which
+    is not necessarily visible to the compiler, guarantees that the requested
+    conversion is value-preserving for the values that can actually occur.
+
+    This is primarily meant for generic code, where the same expression may
+    be value-preserving for one instantiation but not for another, making
+    both @ref safeCast and @ref unsafeCast unusable.
+
+    Unlike @ref safeCast and @ref unsafeCast, this imposes no static check
+    on the type relationship: the caller's claim is about runtime values,
+    not about types.
+*/
+/** @{ */
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_integral_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return static_cast<Dest>(s);
 }
 
+template <typename Dest, typename Src>
+    requires(std::is_enum_v<Dest> && std::is_integral_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return static_cast<Dest>(checkedCast<std::underlying_type_t<Dest>>(s));
+}
+
+template <typename Dest, typename Src>
+    requires(std::is_integral_v<Dest> && std::is_enum_v<Src>)
+constexpr Dest
+checkedCast(Src s) noexcept
+{
+    return checkedCast<Dest>(std::to_underlying(s));
+}
+/** @} */
+
+/** Downcast within a class hierarchy, verified in debug builds.
+
+    Performs a static_cast down a hierarchy, but in debug builds verifies
+    via dynamic_cast that the object's dynamic type actually permits the
+    downcast. Both build modes execute the same conversion; debug builds
+    merely add the check.
+
+    The pointer form passes null through unchanged, as dynamic_cast does.
+
+    @note The check requires @p Src to be polymorphic; in release builds
+          an invalid downcast is undefined behavior on use, exactly as
+          with a bare static_cast.
+*/
+/** @{ */
 template <class Dest, class Src>
-    requires std::is_pointer_v<Dest>
+    requires(
+        std::is_pointer_v<Dest> && std::is_polymorphic_v<Src> &&
+        std::derived_from<std::remove_pointer_t<Dest>, Src> &&
+        (std::is_const_v<std::remove_pointer_t<Dest>> || !std::is_const_v<Src>) &&
+        (std::is_volatile_v<std::remove_pointer_t<Dest>> || !std::is_volatile_v<Src>))
 inline Dest
 safeDowncast(Src* s) noexcept
 {
-#ifdef NDEBUG
+    XRPL_ASSERT(
+        s == nullptr || dynamic_cast<Dest>(s) != nullptr, "xrpl::safeDowncast : valid downcast");
     return static_cast<Dest>(s);  // NOLINT(cppcoreguidelines-pro-type-static-cast-downcast)
-#else
-    auto* result = dynamic_cast<Dest>(s);
-    XRPL_ASSERT(result != nullptr, "xrpl::safeDowncast : pointer downcast is valid");
-    return result;
-#endif
 }
 
 template <class Dest, class Src>
-    requires std::is_lvalue_reference_v<Dest>
+    requires(
+        std::is_lvalue_reference_v<Dest> && std::is_polymorphic_v<Src> &&
+        std::derived_from<std::remove_reference_t<Dest>, Src>)
 inline Dest
 safeDowncast(Src& s) noexcept
 {
-#ifndef NDEBUG
-    XRPL_ASSERT(
-        dynamic_cast<std::add_pointer_t<std::remove_reference_t<Dest>>>(&s) != nullptr,
-        "xrpl::safeDowncast : reference downcast is valid");
-#endif
-    return static_cast<Dest>(s);  // NOLINT(cppcoreguidelines-pro-type-static-cast-downcast)
+    return *safeDowncast<std::add_pointer_t<std::remove_reference_t<Dest>>>(std::addressof(s));
 }
+/** @} */
 
 }  // namespace xrpl

include/xrpl/beast/type_name.h

@@ -1,47 +0,0 @@
-#pragma once
-
-#include <cstdlib>
-#include <string>
-#include <type_traits>
-#include <typeinfo>
-
-#ifndef _MSC_VER
-#include <cxxabi.h>
-#endif
-
-namespace beast {
-
-template <typename T>
-std::string
-typeName()
-{
-    using TR = std::remove_reference_t<T>;
-
-    std::string name = typeid(TR).name();
-
-#ifndef _MSC_VER
-    if (auto s = abi::__cxa_demangle(name.c_str(), nullptr, nullptr, nullptr))
-    {
-        name = s;
-        // NOLINTNEXTLINE(cppcoreguidelines-no-malloc)
-        std::free(s);
-    }
-#endif
-
-    if (std::is_const_v<TR>)
-        name += " const";
-    if (std::is_volatile_v<TR>)
-        name += " volatile";
-    if (std::is_lvalue_reference_v<T>)
-    {
-        name += "&";
-    }
-    else if (std::is_rvalue_reference_v<T>)
-    {
-        name += "&&";
-    }
-
-    return name;
-}
-
-}  // namespace beast

include/xrpl/beast/utility/Zero.h

@@ -2,26 +2,24 @@
 
 #pragma once
 
+#include <compare>
+#include <concepts>
+
 namespace beast {
 
 /**
  * Zero allows classes to offer efficient comparisons to zero.
  *
- * Zero is a struct to allow classes to efficiently compare with zero without
- * requiring an rvalue construction.
- *
  * It's often the case that we have classes which combine a number and a unit.
  * In such cases, comparisons like t > 0 or t != 0 make sense, but comparisons
- * like t > 1 or t != 1 do not.
+ * like t > 1 or t != 1 do not. Comparing against kZero expresses exactly that,
+ * without constructing a T.
  *
- * The class Zero allows such comparisons to be easily made.
- *
- * The comparing class T either needs to have a method called signum() which
- * returns a positive number, 0, or a negative; or there needs to be a signum
- * function which resolves in the namespace which takes an instance of T and
- * returns a positive, zero or negative number.
+ * A type T participates if either `t.signum()` or an unqualified `signum(t)`
+ * found by argument-dependent lookup returns an integer that is negative,
+ * zero, or positive according to the sign of t. Both `t == kZero` and
+ * `kZero == t` work, as do all six relational operators in either order.
  */
-
 struct Zero
 {
     explicit Zero() = default;
@@ -30,115 +28,44 @@ struct Zero
 inline constexpr Zero kZero{};
 
 /**
- * Default implementation of signum calls the method on the class.
+ * Default implementation of signum: call the member function.
  */
-template <typename T>
-auto
-signum(T const& t)
+template <class T>
+    requires requires(T const& t) {
+        { t.signum() } -> std::integral;
+    }
+[[nodiscard]] constexpr auto
+signum(T const& t) noexcept(noexcept(t.signum()))
 {
     return t.signum();
 }
 
-namespace detail::zero_helper {
+namespace detail {
 
-// For argument dependent lookup to function properly, calls to signum must
-// be made from a namespace that does not include overloads of the function..
+/**
+ * A type with a usable signum: either the member-based default above, or a
+ * `signum(t)` overload in T's own namespace, found by ADL. A user overload
+ * that is a better match than the template wins, as usual.
+ */
 template <class T>
-auto
-callSignum(T const& t)
+concept HasSignum = requires(T const& t) {
+    { signum(t) } -> std::integral;
+};
+
+}  // namespace detail
+
+template <detail::HasSignum T>
+[[nodiscard]] constexpr bool
+operator==(T const& t, Zero) noexcept(noexcept(signum(t)))
 {
-    return signum(t);
+    return signum(t) == 0;
 }
 
-}  // namespace detail::zero_helper
-
-// Handle operators where T is on the left side using signum.
-
-template <typename T>
-bool
-operator==(T const& t, Zero)
+template <detail::HasSignum T>
+[[nodiscard]] constexpr std::strong_ordering
+operator<=>(T const& t, Zero) noexcept(noexcept(signum(t)))
 {
-    return detail::zero_helper::callSignum(t) == 0;
-}
-
-template <typename T>
-bool
-operator!=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) != 0;
-}
-
-template <typename T>
-bool
-operator<(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) < 0;
-}
-
-template <typename T>
-bool
-operator>(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) > 0;
-}
-
-template <typename T>
-bool
-operator>=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) >= 0;
-}
-
-template <typename T>
-bool
-operator<=(T const& t, Zero)
-{
-    return detail::zero_helper::callSignum(t) <= 0;
-}
-
-// Handle operators where T is on the right side by
-// reversing the operation, so that T is on the left side.
-
-template <typename T>
-bool
-operator==(Zero, T const& t)
-{
-    return t == kZero;
-}
-
-template <typename T>
-bool
-operator!=(Zero, T const& t)
-{
-    return t != kZero;
-}
-
-template <typename T>
-bool
-operator<(Zero, T const& t)
-{
-    return t > kZero;
-}
-
-template <typename T>
-bool
-operator>(Zero, T const& t)
-{
-    return t < kZero;
-}
-
-template <typename T>
-bool
-operator>=(Zero, T const& t)
-{
-    return t <= kZero;
-}
-
-template <typename T>
-bool
-operator<=(Zero, T const& t)
-{
-    return t >= kZero;
+    return signum(t) <=> 0;
 }
 
 }  // namespace beast

include/xrpl/protocol/AccountID.h

@@ -101,22 +101,6 @@ operator<<(std::ostream& os, AccountID const& x)
     return os;
 }
 
-/**
- * Initialize the global cache used to map AccountID to base58 conversions.
- *
- * The cache is optional and need not be initialized. But because conversion
- * is expensive (it requires a SHA-256 operation) in most cases the overhead
- * of the cache is worth the benefit.
- *
- * @param count The number of entries the cache should accommodate. Zero will
- *              disable the cache, releasing any memory associated with it.
- *
- * @note The function will only initialize the cache the first time it is
- *       invoked. Subsequent invocations do nothing.
- */
-void
-initAccountIdCache(std::size_t count);
-
 }  // namespace xrpl
 
 //------------------------------------------------------------------------------

include/xrpl/protocol/KnownFormats.h

@@ -1,10 +1,10 @@
 #pragma once
 
 #include <xrpl/basics/contract.h>
-#include <xrpl/beast/type_name.h>
 #include <xrpl/protocol/SOTemplate.h>
 
 #include <boost/container/flat_map.hpp>
+#include <boost/core/type_name.hpp>
 
 #include <algorithm>
 #include <cstddef>
@@ -84,7 +84,7 @@ public:
      * Derived classes will load the object with all the known formats.
      */
 private:
-    KnownFormats() : name_(beast::typeName<Derived>())
+    KnownFormats() : name_(boost::core::type_name<Derived>())
     {
     }
 

src/libxrpl/nodestore/backend/RocksDBFactory.cpp

@@ -317,8 +317,8 @@ public:
             }
             else
             {
-                status = static_cast<Status>(
-                    static_cast<int>(Status::CustomCode) + unsafeCast<int>(getStatus.code()));
+                status = checkedCast<Status>(
+                    safeCast<int>(Status::CustomCode) + safeCast<int>(getStatus.code()));
 
                 JLOG(journal.error()) << getStatus.ToString();
             }

src/libxrpl/protocol/AccountID.cpp

@@ -8,6 +8,8 @@
 #include <xrpl/protocol/digest.h>
 #include <xrpl/protocol/tokens.h>
 
+#include <algorithm>
+#include <array>
 #include <atomic>
 #include <cstdint>
 #include <cstring>
@@ -19,85 +21,136 @@
 
 namespace xrpl {
 
-namespace detail {
+namespace {
 
-/**
- * Caches the base58 representations of AccountIDs
+/** If true, we implement a cache for account ID lookups.
+
+    This is generally a good idea and can improve performance, especially
+    when serving client requests.
+
+    The cache may generate warnings under some sanitizers; if you want to
+    disable caching, set this variable to false.
  */
-class AccountIdCache
+constexpr bool cacheAccountIDs = true;
+
+/** Represents a cached entry for the given AccountID.
+
+    We keep the size and alignment of the structure at 64 bytes to
+    make sure it fits within a cache line and avoid false sharing.
+ */
+struct alignas(64) CachedAccountID
 {
-private:
-    struct CachedAccountID
-    {
-        AccountID id;
-        char encoding[40] = {0};
-    };
+    /** The sequence lock for the entry.
 
-    // The actual cache
-    std::vector<CachedAccountID> cache_;
+        An even value means that the data is stable, whereas an odd
+        value indicates the data is being actively modified.
 
-    // We use a hash function designed to resist algorithmic complexity attacks
-    HardenedHash<> hasher_;
+        We use a 32-bit value to ensure that the counter will never
+        return to an observed value during a read window.
+     */
+    std::atomic<std::uint32_t> seq{0};
 
-    // 64 spinlocks, packed into a single 64-bit value
-    std::atomic<std::uint64_t> locks_ = 0;
+    /** The account id. */
+    AccountID id{};
 
-public:
-    AccountIdCache(std::size_t count) : cache_(count)
-    {
-        // This is non-binding, but we try to avoid wasting memory that
-        // is caused by overallocation.
-        cache_.shrink_to_fit();
-    }
+    /** The length of the cached encoding.
 
-    std::string
-    toBase58(AccountID const& id)
-    {
-        auto const index = hasher_(id) % cache_.size();
+        This field disambiguates collisions between ACCOUNT_ZERO and
+        never-written-to slots, since they would otherwise share the
+        same encoded bits.
+     */
+    std::uint8_t len = 0;
 
-        PackedSpinlock sl(locks_, index % 64);
-
-        {
-            std::scoped_lock const lock(sl);
-
-            // The check against the first character of the encoding ensures
-            // that we don't mishandle the case of the all-zero account:
-            if (cache_[index].encoding[0] != 0 && cache_[index].id == id)
-                return cache_[index].encoding;
-        }
-
-        auto ret = encodeBase58Token(TokenType::AccountID, id.data(), id.size());
-
-        XRPL_ASSERT(ret.size() <= 38, "xrpl::detail::AccountIdCache : maximum result size");
-
-        {
-            std::scoped_lock const lock(sl);
-            cache_[index].id = id;
-            std::strcpy(cache_[index].encoding, ret.c_str());
-        }
-
-        return ret;
-    }
+    /** The actual string encoding. */
+    char encoding[39] = {0};
 };
 
-}  // namespace detail
+static_assert(sizeof(CachedAccountID) == 64 && alignof(CachedAccountID) == 64);
 
-static std::unique_ptr<detail::AccountIdCache> gAccountIdCache;
+// The actual cache to use: a simple, direct-mapped, best-effort construct.
+//
+// We do not use a hardened hash for this because an AccountID is already
+// just cryptographically generated (i.e. uniformly distributed) bits and
+// there is no amplification, since collisions do not carry an additional
+// cost.
+//
+// The size is a "nice" power of 2 because it makes the calculation of an
+// index easier.
+constinit std::array<CachedAccountID, 65536> gAccountIdCache{};
 
-void
-initAccountIdCache(std::size_t count)
-{
-    if (!gAccountIdCache && count != 0)
-        gAccountIdCache = std::make_unique<detail::AccountIdCache>(count);
-}
+}  // namespace
 
 std::string
 toBase58(AccountID const& v)
 {
-    if (gAccountIdCache)
-        return gAccountIdCache->toBase58(v);
+    // Since the input bits are generated by a cryptographically secure
+    // hash construct, we can just pick any subset of them, no muss, no
+    // fuss.
+    auto const index = [&v]() -> std::uint16_t {
+        auto const data = v.data();
 
-    return encodeBase58Token(TokenType::AccountID, v.data(), v.size());
+        return static_cast<std::uint16_t>(data[0]) | (static_cast<std::uint16_t>(data[1]) << 8);
+    }();
+
+    if constexpr (cacheAccountIDs)
+    {
+        auto& slot = gAccountIdCache[index];
+
+        // This is the optimistic, store-free read path: a collision with a
+        // concurrent writer will be detected because the seq recheck fails
+        // and we fall through to the slow path.
+        //
+        // These unsynchronized reads of the slot fields are, formally, data
+        // races and, technically speaking, result in undefined behavior and
+        // a tool like TSAN might flag them. These should not have an impact
+        // on the correctness of the returned data: the sequence lock checks
+        // ensure we discard any data that was in flux.
+        if (auto const s0 = slot.seq.load(std::memory_order::acquire);
+            (s0 & 1) == 0 && slot.len != 0 && slot.id == v)
+        {
+            char buf[38];
+            auto const len = std::min<std::size_t>(slot.len, sizeof(buf));
+            std::memcpy(buf, slot.encoding, len);
+
+            // Prevents the loads above from sinking below the recheck; the
+            // acquire on s0 constrains later operations, not earlier ones.
+            std::atomic_thread_fence(std::memory_order::acquire);
+
+            // Everything read from the slot — the gates above and the bytes in
+            // buf — precedes this recheck and is validated by it. No slot access
+            // may follow it.
+            if (slot.seq.load(std::memory_order::relaxed) == s0)
+                return std::string(buf, len);
+        }
+    }
+
+    auto ret = encodeBase58Token(TokenType::AccountID, v.data(), v.size());
+
+    XRPL_ASSERT(!ret.empty() && ret.size() <= 38, "xrpl::toBase58 : maximum result size");
+
+    if constexpr (cacheAccountIDs)
+    {
+        auto& slot = gAccountIdCache[index];
+
+        // The CAS to an odd value excludes other writers; if it fails, another
+        // thread wrote or is writing into this slot. That is not a problem: we
+        // just don't store our result into the cache this time.
+        if (auto s0 = slot.seq.load(std::memory_order::relaxed); (s0 & 1) == 0 &&
+            slot.seq.compare_exchange_strong(s0, s0 + 1, std::memory_order::acquire))
+        {
+            slot.id = v;
+            slot.len = static_cast<std::uint8_t>(ret.size());
+            std::copy_n(ret.data(), ret.size(), slot.encoding);
+
+            // The acquire on the CAS above keeps the writes from becoming visible
+            // before the seqlock transitions to an odd value, which means readers
+            // can detect an in-progress write. This release publishes them before
+            // the seqlock transitions to an even value.
+            slot.seq.store(s0 + 2, std::memory_order::release);
+        }
+    }
+
+    return ret;
 }
 
 template <>

src/xrpld/app/main/Application.cpp

@@ -473,8 +473,6 @@ public:
               getIoContext())
         , grpcServer_(std::make_unique<GRPCServer>(*this))
     {
-        initAccountIdCache(config_->getValueFor(SizedItem::AccountIdCacheSize));
-
         add(resourceManager_.get());
 
         //

src/xrpld/app/misc/FeeVoteImpl.cpp

@@ -226,27 +226,22 @@ FeeVoteImpl::doVoting(
         auto doVote = [](std::shared_ptr<STValidation> const& val,
                          detail::VotableValue& value,
                          auto const& valueField) {
-            if (auto const field = val->at(~valueField))
+            using XRPType = XRPAmount::value_type;
+
+            if (auto const field = val->at(~valueField); field && std::in_range<XRPType>(*field))
             {
-                using XRPType = XRPAmount::value_type;
-                auto const vote = *field;
-                if (vote <= std::numeric_limits<XRPType>::max() &&
-                    isLegalAmountSigned(XRPAmount{unsafeCast<XRPType>(vote)}))
+                if (auto const amount = XRPAmount{checkedCast<XRPType>(*field)};
+                    isLegalAmountSigned(amount))
                 {
-                    value.addVote(XRPAmount{unsafeCast<XRPType>(vote)});
-                }
-                else
-                {
-                    // Invalid amounts will be treated as if they're
-                    // not provided. Don't throw because this value is
-                    // provided by an external entity.
-                    value.noVote();
+                    value.addVote(amount);
+                    return;
                 }
             }
-            else
-            {
-                value.noVote();
-            }
+
+            // Invalid or missing amounts are treated as if they're not
+            // provided. Don't throw because this value is provided by an
+            // external entity.
+            value.noVote();
         };
 
         for (auto const& val : set)

src/xrpld/core/Config.h

@@ -41,7 +41,6 @@ enum class SizedItem : std::size_t {
     OpenFinalLimit,
     BurstSize,
     RamSizeGb,
-    AccountIdCacheSize,
 };
 
 /**

src/xrpld/core/detail/Config.cpp

@@ -111,7 +111,7 @@ namespace xrpl {
 
 // clang-format off
 // The configurable node sizes are "tiny", "small", "medium", "large", "huge"
-inline constexpr std::array<std::pair<SizedItem, std::array<int, 5>>, 13>
+inline constexpr std::array<std::pair<SizedItem, std::array<int, 5>>, 12>
 kSizedItems
 {{
     // FIXME: We should document each of these items, explaining exactly
@@ -130,8 +130,7 @@ kSizedItems
     {SizedItem::LgrDbCache,         {{      4,       8,      16,      32,     128 }}},
     {SizedItem::OpenFinalLimit,     {{      8,      16,      32,      64,     128 }}},
     {SizedItem::BurstSize,          {{      4,       8,      16,      32,      48 }}},
-    {SizedItem::RamSizeGb,          {{      6,       8,      12,      24,       0 }}},
-    {SizedItem::AccountIdCacheSize, {{  20047,   50053,   77081,  150061,  300007 }}}
+    {SizedItem::RamSizeGb,          {{      6,       8,      12,      24,       0 }}}
 }};
 // clang-format on