Merge branch 'main' into zs/ui-show-cook-artifacts

11 files changed, 1738 insertions, 46 deletions

diff --git a/src/zenstore/blockstore.cpp b/src/zenstore/blockstore.cpp
index e976c061d..63c0388fa 100644
--- a/src/zenstore/blockstore.cpp
+++ b/src/zenstore/blockstore.cpp
@@ -578,7 +578,7 @@ BlockStore::WriteChunk(const void* Data, uint64_t Size, uint32_t Alignment, cons
 }
 
 void
-BlockStore::WriteChunks(std::span<IoBuffer> Datas, uint32_t Alignment, const WriteChunksCallback& Callback)
+BlockStore::WriteChunks(std::span<const IoBuffer> Datas, uint32_t Alignment, const WriteChunksCallback& Callback)
 {
 	ZEN_MEMSCOPE(GetBlocksTag());
 	ZEN_TRACE_CPU("BlockStore::WriteChunks");
diff --git a/src/zenstore/buildstore/buildstore.cpp b/src/zenstore/buildstore/buildstore.cpp
new file mode 100644
index 000000000..8674aab75
--- /dev/null
+++ b/src/zenstore/buildstore/buildstore.cpp
@@ -0,0 +1,1475 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zenstore/buildstore/buildstore.h>
+
+#include <zencore/fmtutils.h>
+#include <zencore/logging.h>
+#include <zencore/memory/llm.h>
+#include <zencore/scopeguard.h>
+#include <zencore/trace.h>
+#include <zencore/workthreadpool.h>
+
+#include <zencore/uid.h>
+#include <zencore/xxhash.h>
+
+ZEN_THIRD_PARTY_INCLUDES_START
+#include <gsl/gsl-lite.hpp>
+ZEN_THIRD_PARTY_INCLUDES_END
+
+#if ZEN_WITH_TESTS
+#	include <zencore/compactbinarybuilder.h>
+#	include <zencore/compress.h>
+#	include <zencore/testing.h>
+#	include <zencore/testutils.h>
+#endif	// ZEN_WITH_TESTS
+
+namespace zen {
+const FLLMTag&
+GetBuildstoreTag()
+{
+	static FLLMTag _("store", FLLMTag("builds"));
+
+	return _;
+}
+
+using namespace std::literals;
+
+namespace blobstore::impl {
+
+	const std::string BaseName		 = "builds";
+	const char*		  IndexExtension = ".uidx";
+	const char*		  LogExtension	 = ".slog";
+
+	std::filesystem::path GetBlobIndexPath(const std::filesystem::path& RootDirectory)
+	{
+		return RootDirectory / (BaseName + IndexExtension);
+	}
+
+	std::filesystem::path GetBlobLogPath(const std::filesystem::path& RootDirectory) { return RootDirectory / (BaseName + LogExtension); }
+
+	std::filesystem::path GetMetaIndexPath(const std::filesystem::path& RootDirectory)
+	{
+		return RootDirectory / (BaseName + "_meta" + IndexExtension);
+	}
+
+	std::filesystem::path GetMetaLogPath(const std::filesystem::path& RootDirectory)
+	{
+		return RootDirectory / (BaseName + "_meta" + LogExtension);
+	}
+}  // namespace blobstore::impl
+
+BuildStore::BuildStore(const BuildStoreConfig& Config, GcManager& Gc)
+: m_Config(Config)
+, m_Gc(Gc)
+, m_LargeBlobStore(m_Gc)
+, m_SmallBlobStore(Gc)
+, m_MetadataBlockStore()
+{
+	ZEN_TRACE_CPU("BuildStore::BuildStore");
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+	try
+	{
+		std::filesystem::path BlobLogPath = blobstore::impl::GetBlobLogPath(Config.RootDirectory);
+		std::filesystem::path MetaLogPath = blobstore::impl::GetMetaLogPath(Config.RootDirectory);
+		bool				  IsNew		  = !(std::filesystem::exists(BlobLogPath) && std::filesystem::exists(MetaLogPath));
+
+		if (!IsNew)
+		{
+			m_BlobLogFlushPosition = ReadPayloadLog(RwLock::ExclusiveLockScope(m_Lock), BlobLogPath, 0);
+			m_MetaLogFlushPosition = ReadMetadataLog(RwLock::ExclusiveLockScope(m_Lock), MetaLogPath, 0);
+		}
+		m_LargeBlobStore.Initialize(Config.RootDirectory / "file_cas", IsNew);
+		m_SmallBlobStore.Initialize(Config.RootDirectory,
+									"blob_cas",
+									m_Config.SmallBlobBlockStoreMaxBlockSize,
+									m_Config.SmallBlobBlockStoreAlignement,
+									IsNew);
+		m_MetadataBlockStore.Initialize(Config.RootDirectory / "metadata", m_Config.MetadataBlockStoreMaxBlockSize, 1u << 20);
+		{
+			BlockStore::BlockIndexSet KnownBlocks;
+			for (const BlobEntry& Blob : m_BlobEntries)
+			{
+				if (const MetadataIndex MetaIndex = Blob.Metadata; MetaIndex)
+				{
+					const MetadataEntry& Metadata = m_MetadataEntries[MetaIndex];
+					KnownBlocks.insert(Metadata.Location.BlockIndex);
+				}
+			}
+			m_MetadataBlockStore.SyncExistingBlocksOnDisk(KnownBlocks);
+		}
+
+		m_PayloadlogFile.Open(BlobLogPath, CasLogFile::Mode::kWrite);
+		m_MetadatalogFile.Open(MetaLogPath, CasLogFile::Mode::kWrite);
+
+		m_Gc.AddGcReferencer(*this);
+		m_Gc.AddGcReferenceLocker(*this);
+	}
+	catch (const std::exception& Ex)
+	{
+		ZEN_ERROR("Failed to initialize build store. Reason: '{}'", Ex.what());
+		m_Gc.RemoveGcReferenceLocker(*this);
+		m_Gc.RemoveGcReferencer(*this);
+	}
+}
+
+BuildStore::~BuildStore()
+{
+	try
+	{
+		ZEN_TRACE_CPU("BuildStore::~BuildStore");
+		m_Gc.RemoveGcReferenceLocker(*this);
+		m_Gc.RemoveGcReferencer(*this);
+		Flush();
+		m_MetadatalogFile.Close();
+		m_PayloadlogFile.Close();
+	}
+	catch (const std::exception& Ex)
+	{
+		ZEN_ERROR("~BuildStore() threw exception: {}", Ex.what());
+	}
+}
+
+void
+BuildStore::PutBlob(const IoHash& BlobHash, const IoBuffer& Payload)
+{
+	ZEN_TRACE_CPU("BuildStore::PutBlob");
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+	ZEN_ASSERT(Payload.GetContentType() == ZenContentType::kCompressedBinary);
+	{
+		RwLock::SharedLockScope _(m_Lock);
+		if (auto It = m_BlobLookup.find(BlobHash); It != m_BlobLookup.end())
+		{
+			const BlobIndex BlobIndex = It->second;
+			if (m_BlobEntries[BlobIndex].Payload)
+			{
+				return;
+			}
+		}
+	}
+
+	PayloadEntry Entry;
+	if (Payload.GetSize() > m_Config.SmallBlobBlockStoreMaxBlockEmbedSize)
+	{
+		CasStore::InsertResult Result = m_LargeBlobStore.InsertChunk(Payload, BlobHash);
+		ZEN_UNUSED(Result);
+		Entry = {.Flags = PayloadEntry::kStandalone};
+	}
+	else
+	{
+		CasStore::InsertResult Result = m_SmallBlobStore.InsertChunk(Payload, BlobHash);
+		ZEN_UNUSED(Result);
+		Entry = {.Flags = 0};
+	}
+	m_PayloadlogFile.Append(PayloadDiskEntry{.Entry = Entry, .BlobHash = BlobHash});
+
+	RwLock::ExclusiveLockScope _(m_Lock);
+	if (auto It = m_BlobLookup.find(BlobHash); It != m_BlobLookup.end())
+	{
+		const BlobIndex ExistingBlobIndex = It->second;
+		BlobEntry&		Blob			  = m_BlobEntries[ExistingBlobIndex];
+		if (Blob.Payload)
+		{
+			m_PayloadEntries[Blob.Payload] = Entry;
+		}
+		else
+		{
+			Blob.Payload = PayloadIndex(gsl::narrow<uint32_t>(m_PayloadEntries.size()));
+			m_PayloadEntries.push_back(Entry);
+		}
+		Blob.LastAccessTime = GcClock::TickCount();
+	}
+	else
+	{
+		PayloadIndex NewPayloadIndex = PayloadIndex(gsl::narrow<uint32_t>(m_PayloadEntries.size()));
+		m_PayloadEntries.push_back(Entry);
+
+		const BlobIndex NewBlobIndex(gsl::narrow<uint32_t>(m_BlobEntries.size()));
+		// we only remove during GC and compact this then...
+		m_BlobEntries.push_back(BlobEntry{.Payload = NewPayloadIndex, .LastAccessTime = AccessTime(GcClock::TickCount())});
+		m_BlobLookup.insert({BlobHash, NewBlobIndex});
+	}
+}
+
+IoBuffer
+BuildStore::GetBlob(const IoHash& BlobHash)
+{
+	ZEN_TRACE_CPU("BuildStore::GetBlob");
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+	RwLock::SharedLockScope Lock(m_Lock);
+	if (auto It = m_BlobLookup.find(BlobHash); It != m_BlobLookup.end())
+	{
+		const BlobIndex ExistingBlobIndex = It->second;
+		BlobEntry&		Blob			  = m_BlobEntries[ExistingBlobIndex];
+		Blob.LastAccessTime				  = GcClock::TickCount();
+		if (Blob.Payload)
+		{
+			const PayloadEntry& Entry		 = m_PayloadEntries[Blob.Payload];
+			const bool			IsStandalone = (Entry.Flags & PayloadEntry::kStandalone) != 0;
+			Lock.ReleaseNow();
+
+			IoBuffer Chunk;
+			if (IsStandalone)
+			{
+				ZEN_TRACE_CPU("GetLarge");
+				Chunk = m_LargeBlobStore.FindChunk(BlobHash);
+			}
+			else
+			{
+				ZEN_TRACE_CPU("GetSmall");
+				Chunk = m_SmallBlobStore.FindChunk(BlobHash);
+			}
+			if (Chunk)
+			{
+				Chunk.SetContentType(ZenContentType::kCompressedBinary);
+				return Chunk;
+			}
+			else
+			{
+				ZEN_WARN("Inconsistencies in build store, {} is in index but not {}", BlobHash, IsStandalone ? "on disk" : "in block");
+			}
+		}
+	}
+	return {};
+}
+
+std::vector<BuildStore::BlobExistsResult>
+BuildStore::BlobsExists(std::span<const IoHash> BlobHashes)
+{
+	ZEN_TRACE_CPU("BuildStore::BlobsExists");
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+	std::vector<BuildStore::BlobExistsResult> Result;
+	Result.reserve(BlobHashes.size());
+	RwLock::SharedLockScope _(m_Lock);
+	for (const IoHash& BlobHash : BlobHashes)
+	{
+		if (auto It = m_BlobLookup.find(BlobHash); It != m_BlobLookup.end())
+		{
+			const BlobIndex ExistingBlobIndex = It->second;
+			BlobEntry&		Blob			  = m_BlobEntries[ExistingBlobIndex];
+			bool			HasPayload		  = !!Blob.Payload;
+			bool			HasMetadata		  = !!Blob.Metadata;
+			Result.push_back(BlobExistsResult{.HasBody = HasPayload, .HasMetadata = HasMetadata});
+		}
+		else
+		{
+			Result.push_back({});
+		}
+	}
+	return Result;
+}
+
+void
+BuildStore::PutMetadatas(std::span<const IoHash> BlobHashes, std::span<const IoBuffer> MetaDatas)
+{
+	ZEN_TRACE_CPU("BuildStore::PutMetadatas");
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+	size_t WriteBlobIndex = 0;
+	m_MetadataBlockStore.WriteChunks(MetaDatas, m_Config.MetadataBlockStoreAlignement, [&](std::span<BlockStoreLocation> Locations) {
+		RwLock::ExclusiveLockScope _(m_Lock);
+		for (size_t LocationIndex = 0; LocationIndex < Locations.size(); LocationIndex++)
+		{
+			const IoBuffer&			  Data	   = MetaDatas[WriteBlobIndex];
+			const IoHash&			  BlobHash = BlobHashes[WriteBlobIndex];
+			const BlockStoreLocation& Location = Locations[LocationIndex];
+
+			MetadataEntry Entry = {.Location = Location, .ContentType = Data.GetContentType(), .Flags = 0};
+			m_MetadatalogFile.Append(MetadataDiskEntry{.Entry = Entry, .BlobHash = BlobHash});
+
+			if (auto It = m_BlobLookup.find(BlobHash); It != m_BlobLookup.end())
+			{
+				const BlobIndex ExistingBlobIndex = It->second;
+				BlobEntry&		Blob			  = m_BlobEntries[ExistingBlobIndex];
+				if (Blob.Metadata)
+				{
+					m_MetadataEntries[Blob.Metadata] = Entry;
+				}
+				else
+				{
+					Blob.Metadata = MetadataIndex(gsl::narrow<uint32_t>(m_MetadataEntries.size()));
+					m_MetadataEntries.push_back(Entry);
+				}
+				Blob.LastAccessTime = GcClock::TickCount();
+			}
+			else
+			{
+				MetadataIndex NewMetadataIndex = MetadataIndex(gsl::narrow<uint32_t>(m_MetadataEntries.size()));
+				m_MetadataEntries.push_back(Entry);
+
+				const BlobIndex NewBlobIndex(gsl::narrow<uint32_t>(m_BlobEntries.size()));
+				m_BlobEntries.push_back(BlobEntry{.Metadata = NewMetadataIndex, .LastAccessTime = AccessTime(GcClock::TickCount())});
+				m_BlobLookup.insert({BlobHash, NewBlobIndex});
+			}
+			WriteBlobIndex++;
+			if (m_TrackedCacheKeys)
+			{
+				m_TrackedCacheKeys->insert(BlobHash);
+			}
+		}
+	});
+}
+
+std::vector<IoBuffer>
+BuildStore::GetMetadatas(std::span<const IoHash> BlobHashes, WorkerThreadPool* OptionalWorkerPool)
+{
+	ZEN_TRACE_CPU("BuildStore::GetMetadatas");
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+	std::vector<BlockStoreLocation> MetaLocations;
+	std::vector<size_t>				MetaLocationResultIndexes;
+	MetaLocations.reserve(BlobHashes.size());
+	MetaLocationResultIndexes.reserve(BlobHashes.size());
+	tsl::robin_set<uint32_t> ReferencedBlocks;
+
+	std::vector<IoBuffer>		Result;
+	std::vector<ZenContentType> ResultContentTypes;
+	Result.resize(BlobHashes.size());
+	ResultContentTypes.resize(BlobHashes.size(), ZenContentType::kUnknownContentType);
+	{
+		RwLock::SharedLockScope _(m_Lock);
+		for (size_t Index = 0; Index < BlobHashes.size(); Index++)
+		{
+			const IoHash& BlobHash = BlobHashes[Index];
+			if (auto It = m_BlobLookup.find(BlobHash); It != m_BlobLookup.end())
+			{
+				const BlobIndex ExistingBlobIndex = It->second;
+				BlobEntry&		ExistingBlobEntry = m_BlobEntries[ExistingBlobIndex];
+				if (ExistingBlobEntry.Metadata)
+				{
+					const MetadataEntry& ExistingMetadataEntry = m_MetadataEntries[ExistingBlobEntry.Metadata];
+					MetaLocations.push_back(ExistingMetadataEntry.Location);
+					MetaLocationResultIndexes.push_back(Index);
+					ReferencedBlocks.insert(ExistingMetadataEntry.Location.BlockIndex);
+					ResultContentTypes[Index] = ExistingMetadataEntry.ContentType;
+				}
+				ExistingBlobEntry.LastAccessTime = AccessTime(GcClock::Tick());
+			}
+		}
+	}
+
+	auto DoOneBlock = [&](std::span<const size_t> ChunkIndexes) {
+		if (ChunkIndexes.size() < 4)
+		{
+			for (size_t ChunkIndex : ChunkIndexes)
+			{
+				IoBuffer Chunk = m_MetadataBlockStore.TryGetChunk(MetaLocations[ChunkIndex]);
+				if (Chunk)
+				{
+					size_t ResultIndex	= MetaLocationResultIndexes[ChunkIndex];
+					Result[ResultIndex] = std::move(Chunk);
+				}
+			}
+			return true;
+		}
+		return m_MetadataBlockStore.IterateBlock(
+			MetaLocations,
+			ChunkIndexes,
+			[&](size_t ChunkIndex, const void* Data, uint64_t Size) {
+				if (Data != nullptr)
+				{
+					size_t ResultIndex	= MetaLocationResultIndexes[ChunkIndex];
+					Result[ResultIndex] = IoBuffer(IoBuffer::Clone, Data, Size);
+				}
+				return true;
+			},
+			[&](size_t ChunkIndex, BlockStoreFile& File, uint64_t Offset, uint64_t Size) {
+				size_t ResultIndex	= MetaLocationResultIndexes[ChunkIndex];
+				Result[ResultIndex] = File.GetChunk(Offset, Size);
+				return true;
+			},
+			8u * 1024u);
+	};
+
+	if (!MetaLocations.empty())
+	{
+		Latch WorkLatch(1);
+
+		m_MetadataBlockStore.IterateChunks(MetaLocations, [&](uint32_t BlockIndex, std::span<const size_t> ChunkIndexes) -> bool {
+			ZEN_UNUSED(BlockIndex);
+			if (ChunkIndexes.size() == MetaLocations.size() || OptionalWorkerPool == nullptr || ReferencedBlocks.size() == 1)
+			{
+				return DoOneBlock(ChunkIndexes);
+			}
+			else
+			{
+				ZEN_ASSERT(OptionalWorkerPool != nullptr);
+				WorkLatch.AddCount(1);
+				try
+				{
+					OptionalWorkerPool->ScheduleWork([&, ChunkIndexes = std::vector<size_t>(ChunkIndexes.begin(), ChunkIndexes.end())]() {
+						auto _ = MakeGuard([&WorkLatch]() { WorkLatch.CountDown(); });
+						try
+						{
+							DoOneBlock(ChunkIndexes);
+						}
+						catch (const std::exception& Ex)
+						{
+							ZEN_WARN("Failed getting metadata for {} chunks. Reason: {}", ChunkIndexes.size(), Ex.what());
+						}
+					});
+				}
+				catch (const std::exception& Ex)
+				{
+					WorkLatch.CountDown();
+					ZEN_ERROR("Failed dispatching async work to fetch metadata for {} chunks. Reason: {}", ChunkIndexes.size(), Ex.what());
+				}
+				return true;
+			}
+		});
+
+		WorkLatch.CountDown();
+		WorkLatch.Wait();
+	}
+	for (size_t Index = 0; Index < Result.size(); Index++)
+	{
+		if (Result[Index])
+		{
+			Result[Index].SetContentType(ResultContentTypes[Index]);
+		}
+	}
+	return Result;
+}
+
+void
+BuildStore::Flush()
+{
+	ZEN_TRACE_CPU("BuildStore::Flush");
+	try
+	{
+		m_LargeBlobStore.Flush();
+		m_SmallBlobStore.Flush();
+		m_MetadataBlockStore.Flush(false);
+
+		m_PayloadlogFile.Flush();
+		m_MetadatalogFile.Flush();
+	}
+	catch (const std::exception& Ex)
+	{
+		ZEN_ERROR("BuildStore::Flush failed. Reason: {}", Ex.what());
+	}
+}
+
+void
+BuildStore::CompactState()
+{
+	ZEN_TRACE_CPU("BuildStore::CompactState");
+
+	std::vector<BlobEntry>	   BlobEntries;
+	std::vector<PayloadEntry>  PayloadEntries;
+	std::vector<MetadataEntry> MetadataEntries;
+
+	tsl::robin_map<IoHash, BlobIndex, IoHash::Hasher> BlobLookup;
+
+	RwLock::ExclusiveLockScope _(m_Lock);
+	const size_t			   EntryCount = m_BlobLookup.size();
+	BlobLookup.reserve(EntryCount);
+	const size_t PayloadCount = m_PayloadEntries.size();
+	PayloadEntries.reserve(PayloadCount);
+	const size_t MetadataCount = m_MetadataEntries.size();
+	MetadataEntries.reserve(MetadataCount);
+
+	for (auto LookupIt : m_BlobLookup)
+	{
+		const IoHash&	 BlobHash	   = LookupIt.first;
+		const BlobIndex	 ReadBlobIndex = LookupIt.second;
+		const BlobEntry& ReadBlobEntry = m_BlobEntries[ReadBlobIndex];
+
+		const BlobIndex WriteBlobIndex(gsl::narrow<uint32_t>(BlobEntries.size()));
+		BlobEntries.push_back(ReadBlobEntry);
+		BlobEntry& WriteBlobEntry = BlobEntries.back();
+
+		if (WriteBlobEntry.Payload)
+		{
+			const PayloadEntry& ReadPayloadEntry = m_PayloadEntries[ReadBlobEntry.Payload];
+			WriteBlobEntry.Payload				 = PayloadIndex(gsl::narrow<uint32_t>(PayloadEntries.size()));
+			PayloadEntries.push_back(ReadPayloadEntry);
+		}
+		if (ReadBlobEntry.Metadata)
+		{
+			const MetadataEntry& ReadMetadataEntry = m_MetadataEntries[ReadBlobEntry.Metadata];
+			WriteBlobEntry.Metadata				   = MetadataIndex(gsl::narrow<uint32_t>(MetadataEntries.size()));
+			MetadataEntries.push_back(ReadMetadataEntry);
+		}
+
+		BlobLookup.insert({BlobHash, WriteBlobIndex});
+	}
+	m_BlobEntries.swap(BlobEntries);
+	m_PayloadEntries.swap(PayloadEntries);
+	m_MetadataEntries.swap(MetadataEntries);
+	m_BlobLookup.swap(BlobLookup);
+}
+
+uint64_t
+BuildStore::ReadPayloadLog(const RwLock::ExclusiveLockScope&, const std::filesystem::path& LogPath, uint64_t SkipEntryCount)
+{
+	ZEN_TRACE_CPU("BuildStore::ReadPayloadLog");
+	if (!std::filesystem::is_regular_file(LogPath))
+	{
+		return 0;
+	}
+
+	uint64_t   LogEntryCount = 0;
+	Stopwatch  Timer;
+	const auto _ = MakeGuard([&] {
+		ZEN_INFO("read build store '{}' payload log containing {} entries in {}",
+				 LogPath,
+				 LogEntryCount,
+				 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+	});
+
+	TCasLogFile<PayloadDiskEntry> CasLog;
+	if (!CasLog.IsValid(LogPath))
+	{
+		std::filesystem::remove(LogPath);
+		return 0;
+	}
+	CasLog.Open(LogPath, CasLogFile::Mode::kRead);
+	if (!CasLog.Initialize())
+	{
+		return 0;
+	}
+
+	const uint64_t EntryCount = CasLog.GetLogCount();
+	if (EntryCount < SkipEntryCount)
+	{
+		ZEN_WARN("reading full payload log at '{}', reason: Log position from index snapshot is out of range", LogPath);
+		SkipEntryCount = 0;
+	}
+
+	LogEntryCount			   = EntryCount - SkipEntryCount;
+	uint64_t InvalidEntryCount = 0;
+
+	CasLog.Replay(
+		[&](const PayloadDiskEntry& Record) {
+			std::string InvalidEntryReason;
+			if (Record.Entry.Flags & PayloadEntry::kTombStone)
+			{
+				// Note: this leaves m_BlobLookup and other arrays with 'holes' in them, this will get clean up in compact gc operation
+				m_BlobLookup.erase(Record.BlobHash);
+				return;
+			}
+
+			if (!ValidatePayloadDiskEntry(Record, InvalidEntryReason))
+			{
+				ZEN_WARN("skipping invalid payload entry in '{}', reason: '{}'", LogPath, InvalidEntryReason);
+				++InvalidEntryCount;
+				return;
+			}
+			if (auto It = m_BlobLookup.find(Record.BlobHash); It != m_BlobLookup.end())
+			{
+				const BlobIndex ExistingBlobIndex = It->second;
+				BlobEntry&		ExistingBlob	  = m_BlobEntries[ExistingBlobIndex];
+				if (ExistingBlob.Payload)
+				{
+					const PayloadIndex ExistingPayloadIndex = ExistingBlob.Payload;
+					m_PayloadEntries[ExistingPayloadIndex]	= Record.Entry;
+				}
+				else
+				{
+					const PayloadIndex NewPayloadIndex(gsl::narrow<uint32_t>(m_PayloadEntries.size()));
+					m_PayloadEntries.push_back(Record.Entry);
+					ExistingBlob.Payload = NewPayloadIndex;
+				}
+			}
+			else
+			{
+				const PayloadIndex NewPayloadIndex(gsl::narrow<uint32_t>(m_PayloadEntries.size()));
+				m_PayloadEntries.push_back(Record.Entry);
+
+				const BlobIndex NewBlobIndex(gsl::narrow<uint32_t>(m_BlobEntries.size()));
+				m_BlobEntries.push_back(BlobEntry{.Payload = NewPayloadIndex, .LastAccessTime = AccessTime(GcClock::Tick())});
+				m_BlobLookup.insert_or_assign(Record.BlobHash, NewBlobIndex);
+			}
+		},
+		SkipEntryCount);
+
+	if (InvalidEntryCount)
+	{
+		ZEN_WARN("found {} invalid payload entries in '{}'", InvalidEntryCount, LogPath);
+	}
+
+	return LogEntryCount;
+}
+
+uint64_t
+BuildStore::ReadMetadataLog(const RwLock::ExclusiveLockScope&, const std::filesystem::path& LogPath, uint64_t SkipEntryCount)
+{
+	ZEN_TRACE_CPU("BuildStore::ReadMetadataLog");
+	if (!std::filesystem::is_regular_file(LogPath))
+	{
+		return 0;
+	}
+
+	uint64_t   LogEntryCount = 0;
+	Stopwatch  Timer;
+	const auto _ = MakeGuard([&] {
+		ZEN_INFO("read build store '{}' metadata log containing {} entries in {}",
+				 LogPath,
+				 LogEntryCount,
+				 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+	});
+
+	TCasLogFile<MetadataDiskEntry> CasLog;
+	if (!CasLog.IsValid(LogPath))
+	{
+		std::filesystem::remove(LogPath);
+		return 0;
+	}
+	CasLog.Open(LogPath, CasLogFile::Mode::kRead);
+	if (!CasLog.Initialize())
+	{
+		return 0;
+	}
+
+	const uint64_t EntryCount = CasLog.GetLogCount();
+	if (EntryCount < SkipEntryCount)
+	{
+		ZEN_WARN("reading full metadata log at '{}', reason: Log position from index snapshot is out of range", LogPath);
+		SkipEntryCount = 0;
+	}
+
+	LogEntryCount			   = EntryCount - SkipEntryCount;
+	uint64_t InvalidEntryCount = 0;
+
+	CasLog.Replay(
+		[&](const MetadataDiskEntry& Record) {
+			std::string InvalidEntryReason;
+			if (Record.Entry.Flags & MetadataEntry::kTombStone)
+			{
+				// Note: this leaves m_BlobLookup and other arrays with 'holes' in them, this will get clean up in compact gc operation
+				m_BlobLookup.erase(Record.BlobHash);
+				return;
+			}
+
+			if (!ValidateMetadataDiskEntry(Record, InvalidEntryReason))
+			{
+				ZEN_WARN("skipping invalid metadata entry in '{}', reason: '{}'", LogPath, InvalidEntryReason);
+				++InvalidEntryCount;
+				return;
+			}
+			if (auto It = m_BlobLookup.find(Record.BlobHash); It != m_BlobLookup.end())
+			{
+				const BlobIndex ExistingBlobIndex = It->second;
+				BlobEntry&		ExistingBlob	  = m_BlobEntries[ExistingBlobIndex];
+				if (ExistingBlob.Metadata)
+				{
+					const MetadataIndex ExistingMetadataIndex = ExistingBlob.Metadata;
+					m_MetadataEntries[ExistingMetadataIndex]  = Record.Entry;
+				}
+				else
+				{
+					const MetadataIndex NewMetadataIndex(gsl::narrow<uint32_t>(m_MetadataEntries.size()));
+					m_MetadataEntries.push_back(Record.Entry);
+					ExistingBlob.Metadata = NewMetadataIndex;
+				}
+			}
+			else
+			{
+				const MetadataIndex NewMetadataIndex(gsl::narrow<uint32_t>(m_MetadataEntries.size()));
+				m_MetadataEntries.push_back(Record.Entry);
+
+				const BlobIndex NewBlobIndex(gsl::narrow<uint32_t>(m_BlobEntries.size()));
+				m_BlobEntries.push_back(BlobEntry{.Metadata = NewMetadataIndex, .LastAccessTime = AccessTime(GcClock::Tick())});
+				m_BlobLookup.insert_or_assign(Record.BlobHash, NewBlobIndex);
+			}
+		},
+		SkipEntryCount);
+
+	if (InvalidEntryCount)
+	{
+		ZEN_WARN("found {} invalid metadata entries in '{}'", InvalidEntryCount, LogPath);
+	}
+
+	return LogEntryCount;
+}
+
+bool
+BuildStore::ValidatePayloadDiskEntry(const PayloadDiskEntry& Entry, std::string& OutReason)
+{
+	if (Entry.BlobHash == IoHash::Zero)
+	{
+		OutReason = fmt::format("Invalid blob hash {}", Entry.BlobHash.ToHexString());
+		return false;
+	}
+	if (Entry.Entry.Flags & ~(PayloadEntry::kTombStone | PayloadEntry::kStandalone))
+	{
+		OutReason = fmt::format("Invalid flags {} for entry {}", Entry.Entry.Flags, Entry.BlobHash.ToHexString());
+		return false;
+	}
+	if (Entry.Entry.Flags & PayloadEntry::kTombStone)
+	{
+		return true;
+	}
+	if (Entry.Entry.Reserved1 != 0 || Entry.Entry.Reserved2 != 0 || Entry.Entry.Reserved3 != 0)
+	{
+		OutReason = fmt::format("Invalid reserved fields for meta entry {}", Entry.BlobHash.ToHexString());
+		return false;
+	}
+	return true;
+}
+
+bool
+BuildStore::ValidateMetadataDiskEntry(const MetadataDiskEntry& Entry, std::string& OutReason)
+{
+	if (Entry.BlobHash == IoHash::Zero)
+	{
+		OutReason = fmt::format("Invalid blob hash {} for meta entry", Entry.BlobHash.ToHexString());
+		return false;
+	}
+	if (Entry.Entry.Location.Size == 0)
+	{
+		OutReason = fmt::format("Invalid meta blob size {} for meta entry", Entry.Entry.Location.Size);
+		return false;
+	}
+	if (Entry.Entry.Reserved1 != 0 || Entry.Entry.Reserved2 != 0)
+	{
+		OutReason = fmt::format("Invalid reserved fields for meta entry {}", Entry.BlobHash.ToHexString());
+		return false;
+	}
+	if (Entry.Entry.Flags & MetadataEntry::kTombStone)
+	{
+		return true;
+	}
+	if (Entry.Entry.ContentType == ZenContentType::kCOUNT)
+	{
+		OutReason = fmt::format("Invalid content type for meta entry {}", Entry.BlobHash.ToHexString());
+		return false;
+	}
+	if (Entry.Reserved1 != 0 || Entry.Reserved2 != 0 || Entry.Reserved3 != 0 || Entry.Reserved4 != 0)
+	{
+		OutReason = fmt::format("Invalid reserved fields for meta entry {}", Entry.BlobHash.ToHexString());
+		return false;
+	}
+	return true;
+}
+
+class BuildStoreGcReferenceChecker : public GcReferenceChecker
+{
+public:
+	BuildStoreGcReferenceChecker(BuildStore& Store) : m_Store(Store) {}
+	virtual std::string GetGcName(GcCtx& Ctx) override
+	{
+		ZEN_UNUSED(Ctx);
+		return fmt::format("buildstore: '{}'", m_Store.m_Config.RootDirectory.string());
+	}
+
+	virtual void PreCache(GcCtx& Ctx) override { ZEN_UNUSED(Ctx); }
+
+	virtual void UpdateLockedState(GcCtx& Ctx) override
+	{
+		ZEN_TRACE_CPU("Builds::UpdateLockedState");
+		ZEN_MEMSCOPE(GetBuildstoreTag());
+
+		auto Log = [&Ctx]() { return Ctx.Logger; };
+
+		m_References.reserve(m_Store.m_BlobLookup.size());
+		for (const auto& It : m_Store.m_BlobLookup)
+		{
+			const BuildStore::BlobIndex ExistingBlobIndex = It.second;
+			if (m_Store.m_BlobEntries[ExistingBlobIndex].Payload)
+			{
+				m_References.push_back(It.first);
+			}
+		}
+		FilterReferences(Ctx, fmt::format("buildstore [LOCKSTATE] '{}'", "buildstore"), m_References);
+	}
+
+	virtual std::span<IoHash> GetUnusedReferences(GcCtx& Ctx, std::span<IoHash> IoCids) override
+	{
+		ZEN_UNUSED(Ctx);
+		ZEN_TRACE_CPU("Builds::GetUnusedReferences");
+		ZEN_MEMSCOPE(GetBuildstoreTag());
+
+		auto Log = [&Ctx]() { return Ctx.Logger; };
+
+		size_t InitialCount = IoCids.size();
+		size_t UsedCount	= InitialCount;
+
+		Stopwatch  Timer;
+		const auto _ = MakeGuard([&] {
+			if (!Ctx.Settings.Verbose)
+			{
+				return;
+			}
+			ZEN_INFO("GCV2: buildstore [FILTER REFERENCES] '{}': filtered out {} used references out of {} in {}",
+					 "buildstore",
+					 UsedCount,
+					 InitialCount,
+					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+		});
+
+		std::span<IoHash> UnusedReferences = KeepUnusedReferences(m_References, IoCids);
+		UsedCount						   = IoCids.size() - UnusedReferences.size();
+		return UnusedReferences;
+	}
+
+private:
+	BuildStore&			m_Store;
+	std::vector<IoHash> m_References;
+};
+
+std::string
+BuildStore::GetGcName(GcCtx& Ctx)
+{
+	ZEN_UNUSED(Ctx);
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+
+	return fmt::format("buildstore: '{}'", m_Config.RootDirectory.string());
+}
+
+class BuildStoreGcCompator : public GcStoreCompactor
+{
+	using BlobEntry			= BuildStore::BlobEntry;
+	using PayloadEntry		= BuildStore::PayloadEntry;
+	using MetadataEntry		= BuildStore::MetadataEntry;
+	using MetadataDiskEntry = BuildStore::MetadataDiskEntry;
+	using BlobIndex			= BuildStore::BlobIndex;
+	using PayloadIndex		= BuildStore::PayloadIndex;
+	using MetadataIndex		= BuildStore::MetadataIndex;
+
+public:
+	BuildStoreGcCompator(BuildStore& Store, std::vector<IoHash>&& RemovedBlobs) : m_Store(Store), m_RemovedBlobs(std::move(RemovedBlobs)) {}
+
+	virtual void CompactStore(GcCtx& Ctx, GcCompactStoreStats& Stats, const std::function<uint64_t()>& ClaimDiskReserveCallback) override
+	{
+		ZEN_UNUSED(ClaimDiskReserveCallback);
+		ZEN_TRACE_CPU("Builds::CompactStore");
+		ZEN_MEMSCOPE(GetBuildstoreTag());
+
+		auto Log = [&Ctx]() { return Ctx.Logger; };
+
+		Stopwatch  Timer;
+		const auto _ = MakeGuard([&] {
+			if (!Ctx.Settings.Verbose)
+			{
+				return;
+			}
+			ZEN_INFO("GCV2: buildstore [COMPACT] '{}': RemovedDisk: {} in {}",
+					 m_Store.m_Config.RootDirectory,
+					 NiceBytes(Stats.RemovedDisk),
+					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+		});
+
+		if (!m_RemovedBlobs.empty())
+		{
+			if (Ctx.Settings.CollectSmallObjects)
+			{
+				m_Store.m_Lock.WithExclusiveLock([this]() { m_Store.m_TrackedCacheKeys = std::make_unique<HashSet>(); });
+				auto __ = MakeGuard([this]() { m_Store.m_Lock.WithExclusiveLock([&]() { m_Store.m_TrackedCacheKeys.reset(); }); });
+
+				BlockStore::BlockUsageMap BlockUsage;
+				{
+					RwLock::SharedLockScope __(m_Store.m_Lock);
+
+					for (auto LookupIt : m_Store.m_BlobLookup)
+					{
+						const BlobIndex	 ReadBlobIndex = LookupIt.second;
+						const BlobEntry& ReadBlobEntry = m_Store.m_BlobEntries[ReadBlobIndex];
+
+						if (ReadBlobEntry.Metadata)
+						{
+							const MetadataEntry& ReadMetadataEntry = m_Store.m_MetadataEntries[ReadBlobEntry.Metadata];
+
+							uint32_t BlockIndex = ReadMetadataEntry.Location.BlockIndex;
+							uint64_t ChunkSize	= RoundUp(ReadMetadataEntry.Location.Size, m_Store.m_Config.MetadataBlockStoreAlignement);
+
+							if (auto BlockUsageIt = BlockUsage.find(BlockIndex); BlockUsageIt != BlockUsage.end())
+							{
+								BlockStore::BlockUsageInfo& Info = BlockUsageIt.value();
+								Info.EntryCount++;
+								Info.DiskUsage += ChunkSize;
+							}
+							else
+							{
+								BlockUsage.insert_or_assign(BlockIndex,
+															BlockStore::BlockUsageInfo{.DiskUsage = ChunkSize, .EntryCount = 1});
+							}
+						}
+					}
+				}
+
+				BlockStore::BlockEntryCountMap BlocksToCompact = m_Store.m_MetadataBlockStore.GetBlocksToCompact(BlockUsage, 90);
+				BlockStoreCompactState		   BlockCompactState;
+				std::vector<IoHash>			   BlockCompactStateKeys;
+				BlockCompactState.IncludeBlocks(BlocksToCompact);
+
+				if (BlocksToCompact.size() > 0)
+				{
+					{
+						RwLock::SharedLockScope ___(m_Store.m_Lock);
+						for (const auto& Entry : m_Store.m_BlobLookup)
+						{
+							BlobIndex Index = Entry.second;
+
+							if (MetadataIndex Meta = m_Store.m_BlobEntries[Index].Metadata; Meta)
+							{
+								if (BlockCompactState.AddKeepLocation(m_Store.m_MetadataEntries[Meta].Location))
+								{
+									BlockCompactStateKeys.push_back(Entry.first);
+								}
+							}
+						}
+					}
+
+					if (Ctx.Settings.IsDeleteMode)
+					{
+						if (Ctx.Settings.Verbose)
+						{
+							ZEN_INFO("GCV2: buildstore [COMPACT] '{}': compacting {} blocks",
+									 m_Store.m_Config.RootDirectory,
+									 BlocksToCompact.size());
+						}
+
+						m_Store.m_MetadataBlockStore.CompactBlocks(
+							BlockCompactState,
+							m_Store.m_Config.MetadataBlockStoreAlignement,
+							[&](const BlockStore::MovedChunksArray& MovedArray, uint64_t FreedDiskSpace) {
+								std::vector<MetadataDiskEntry> MovedEntries;
+								MovedEntries.reserve(MovedArray.size());
+								RwLock::ExclusiveLockScope _(m_Store.m_Lock);
+								for (const std::pair<size_t, BlockStoreLocation>& Moved : MovedArray)
+								{
+									size_t		  ChunkIndex = Moved.first;
+									const IoHash& Key		 = BlockCompactStateKeys[ChunkIndex];
+
+									ZEN_ASSERT(m_Store.m_TrackedCacheKeys);
+									if (m_Store.m_TrackedCacheKeys->contains(Key))
+									{
+										continue;
+									}
+
+									if (auto It = m_Store.m_BlobLookup.find(Key); It != m_Store.m_BlobLookup.end())
+									{
+										const BlobIndex Index = It->second;
+
+										if (MetadataIndex Meta = m_Store.m_BlobEntries[Index].Metadata; Meta)
+										{
+											m_Store.m_MetadataEntries[Meta].Location = Moved.second;
+											MovedEntries.push_back(
+												MetadataDiskEntry{.Entry = m_Store.m_MetadataEntries[Meta], .BlobHash = Key});
+										}
+									}
+								}
+								m_Store.m_MetadatalogFile.Append(MovedEntries);
+								Stats.RemovedDisk += FreedDiskSpace;
+								if (Ctx.IsCancelledFlag.load())
+								{
+									return false;
+								}
+								return true;
+							},
+							ClaimDiskReserveCallback,
+							fmt::format("GCV2: buildstore [COMPACT] '{}': ", m_Store.m_Config.RootDirectory));
+					}
+					else
+					{
+						if (Ctx.Settings.Verbose)
+						{
+							ZEN_INFO("GCV2: buildstore [COMPACT] '{}': skipped compacting of {} eligible blocks",
+									 m_Store.m_Config.RootDirectory,
+									 BlocksToCompact.size());
+						}
+					}
+				}
+			}
+		}
+	}
+
+	virtual std::string GetGcName(GcCtx& Ctx) override
+	{
+		ZEN_UNUSED(Ctx);
+		ZEN_MEMSCOPE(GetBuildstoreTag());
+
+		return fmt::format("buildstore: '{}'", m_Store.m_Config.RootDirectory.string());
+	}
+
+private:
+	BuildStore&				  m_Store;
+	const std::vector<IoHash> m_RemovedBlobs;
+};
+
+GcStoreCompactor*
+BuildStore::RemoveExpiredData(GcCtx& Ctx, GcStats& Stats)
+{
+	ZEN_TRACE_CPU("Builds::RemoveExpiredData");
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+
+	auto Log = [&Ctx]() { return Ctx.Logger; };
+
+	Stopwatch  Timer;
+	const auto _ = MakeGuard([&] {
+		if (Ctx.Settings.Verbose)
+		{
+			ZEN_INFO("GCV2: buildstore [REMOVE EXPIRED] '{}': Count: {}, Expired: {}, Deleted: {}, FreedMemory: {} in {}",
+					 m_Config.RootDirectory,
+					 Stats.CheckedCount,
+					 Stats.FoundCount,
+					 Stats.DeletedCount,
+					 NiceBytes(Stats.FreedMemory),
+					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+		}
+	});
+
+	const GcClock::Tick ExpireTicks = Ctx.Settings.BuildStoreExpireTime.time_since_epoch().count();
+
+	std::vector<IoHash> ExpiredBlobs;
+	{
+		RwLock::SharedLockScope __(m_Lock);
+		for (const auto& It : m_BlobLookup)
+		{
+			const BlobIndex	 ReadBlobIndex = It.second;
+			const BlobEntry& ReadBlobEntry = m_BlobEntries[ReadBlobIndex];
+
+			const GcClock::Tick AccessTick = ReadBlobEntry.LastAccessTime;
+			if (AccessTick < ExpireTicks)
+			{
+				ExpiredBlobs.push_back(It.first);
+			}
+		}
+		Stats.CheckedCount += m_BlobLookup.size();
+		Stats.FoundCount += ExpiredBlobs.size();
+	}
+
+	std::vector<IoHash> RemovedBlobs;
+	if (!ExpiredBlobs.empty())
+	{
+		if (Ctx.Settings.IsDeleteMode)
+		{
+			RemovedBlobs.reserve(ExpiredBlobs.size());
+
+			std::vector<PayloadDiskEntry>  RemovedPayloads;
+			std::vector<MetadataDiskEntry> RemoveMetadatas;
+
+			RwLock::ExclusiveLockScope __(m_Lock);
+			if (Ctx.IsCancelledFlag.load())
+			{
+				return nullptr;
+			}
+
+			for (const IoHash& ExpiredBlob : ExpiredBlobs)
+			{
+				if (auto It = m_BlobLookup.find(ExpiredBlob); It != m_BlobLookup.end())
+				{
+					const BlobIndex	 ReadBlobIndex = It->second;
+					const BlobEntry& ReadBlobEntry = m_BlobEntries[ReadBlobIndex];
+
+					const GcClock::Tick AccessTick = ReadBlobEntry.LastAccessTime;
+
+					if (AccessTick < ExpireTicks)
+					{
+						if (ReadBlobEntry.Payload)
+						{
+							RemovedPayloads.push_back(
+								PayloadDiskEntry{.Entry = m_PayloadEntries[ReadBlobEntry.Payload], .BlobHash = ExpiredBlob});
+							RemovedPayloads.back().Entry.Flags |= PayloadEntry::kTombStone;
+							m_PayloadEntries[ReadBlobEntry.Payload] = {};
+							m_BlobEntries[ReadBlobIndex].Payload	= {};
+						}
+						if (ReadBlobEntry.Metadata)
+						{
+							RemoveMetadatas.push_back(
+								MetadataDiskEntry{.Entry = m_MetadataEntries[ReadBlobEntry.Metadata], .BlobHash = ExpiredBlob});
+							RemoveMetadatas.back().Entry.Flags |= MetadataEntry::kTombStone;
+							m_MetadataEntries[ReadBlobEntry.Metadata] = {};
+							m_BlobEntries[ReadBlobIndex].Metadata	  = {};
+						}
+
+						m_BlobLookup.erase(It);
+
+						RemovedBlobs.push_back(ExpiredBlob);
+						Stats.DeletedCount++;
+					}
+				}
+			}
+			if (!RemovedPayloads.empty())
+			{
+				m_PayloadlogFile.Append(RemovedPayloads);
+			}
+			if (!RemoveMetadatas.empty())
+			{
+				m_MetadatalogFile.Append(RemoveMetadatas);
+			}
+		}
+	}
+
+	if (!RemovedBlobs.empty())
+	{
+		CompactState();
+	}
+
+	return new BuildStoreGcCompator(*this, std::move(RemovedBlobs));
+}
+
+std::vector<GcReferenceChecker*>
+BuildStore::CreateReferenceCheckers(GcCtx& Ctx)
+{
+	ZEN_UNUSED(Ctx);
+	ZEN_MEMSCOPE(GetBuildstoreTag());
+	return {new BuildStoreGcReferenceChecker(*this)};
+}
+
+std::vector<GcReferenceValidator*>
+BuildStore::CreateReferenceValidators(GcCtx& Ctx)
+{
+	ZEN_UNUSED(Ctx);
+	return {};
+}
+
+std::vector<RwLock::SharedLockScope>
+BuildStore::LockState(GcCtx& Ctx)
+{
+	ZEN_UNUSED(Ctx);
+	std::vector<RwLock::SharedLockScope> Locks;
+	Locks.emplace_back(RwLock::SharedLockScope(m_Lock));
+	return Locks;
+}
+
+/*
+		___________              __
+		\__    ___/___   _______/  |_  ______
+		  |    |_/ __ \ /  ___/\   __\/  ___/
+		  |    |\  ___/ \___ \  |  |  \___ \
+		  |____| \___  >____  > |__| /____  >
+					 \/     \/            \/
+*/
+
+#if ZEN_WITH_TESTS
+
+TEST_CASE("BuildStore.Blobs")
+{
+	ScopedTemporaryDirectory _;
+
+	BuildStoreConfig Config;
+	Config.RootDirectory = _.Path() / "build_store";
+
+	std::vector<IoHash> CompressedBlobsHashes;
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+
+		for (size_t I = 0; I < 5; I++)
+		{
+			IoBuffer		 Blob			= CreateSemiRandomBlob(4711 + I * 7);
+			CompressedBuffer CompressedBlob = CompressedBuffer::Compress(SharedBuffer(std::move(Blob)));
+			CompressedBlobsHashes.push_back(CompressedBlob.DecodeRawHash());
+			IoBuffer Payload = std::move(CompressedBlob).GetCompressed().Flatten().AsIoBuffer();
+			Payload.SetContentType(ZenContentType::kCompressedBinary);
+
+			Store.PutBlob(CompressedBlobsHashes.back(), Payload);
+		}
+
+		for (const IoHash& RawHash : CompressedBlobsHashes)
+		{
+			IoBuffer Payload = Store.GetBlob(RawHash);
+			CHECK(Payload);
+			CHECK(Payload.GetContentType() == ZenContentType::kCompressedBinary);
+			IoHash			 VerifyRawHash;
+			uint64_t		 VerifyRawSize;
+			CompressedBuffer CompressedBlob =
+				CompressedBuffer::FromCompressed(SharedBuffer(std::move(Payload)), VerifyRawHash, VerifyRawSize);
+			CHECK(CompressedBlob);
+			CHECK(VerifyRawHash == RawHash);
+			IoBuffer Decompressed = CompressedBlob.Decompress().AsIoBuffer();
+			CHECK(IoHash::HashBuffer(Decompressed) == RawHash);
+		}
+	}
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+		for (const IoHash& RawHash : CompressedBlobsHashes)
+		{
+			IoBuffer Payload = Store.GetBlob(RawHash);
+			CHECK(Payload);
+			CHECK(Payload.GetContentType() == ZenContentType::kCompressedBinary);
+			IoHash			 VerifyRawHash;
+			uint64_t		 VerifyRawSize;
+			CompressedBuffer CompressedBlob =
+				CompressedBuffer::FromCompressed(SharedBuffer(std::move(Payload)), VerifyRawHash, VerifyRawSize);
+			CHECK(CompressedBlob);
+			CHECK(VerifyRawHash == RawHash);
+			IoBuffer Decompressed = CompressedBlob.Decompress().AsIoBuffer();
+			CHECK(IoHash::HashBuffer(Decompressed) == RawHash);
+		}
+
+		for (size_t I = 0; I < 5; I++)
+		{
+			IoBuffer		 Blob			= CreateSemiRandomBlob(5713 + I * 7);
+			CompressedBuffer CompressedBlob = CompressedBuffer::Compress(SharedBuffer(std::move(Blob)));
+			CompressedBlobsHashes.push_back(CompressedBlob.DecodeRawHash());
+			IoBuffer Payload = std::move(CompressedBlob).GetCompressed().Flatten().AsIoBuffer();
+			Payload.SetContentType(ZenContentType::kCompressedBinary);
+
+			Store.PutBlob(CompressedBlobsHashes.back(), Payload);
+		}
+	}
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+		for (const IoHash& RawHash : CompressedBlobsHashes)
+		{
+			IoBuffer Payload = Store.GetBlob(RawHash);
+			CHECK(Payload);
+			CHECK(Payload.GetContentType() == ZenContentType::kCompressedBinary);
+			IoHash			 VerifyRawHash;
+			uint64_t		 VerifyRawSize;
+			CompressedBuffer CompressedBlob =
+				CompressedBuffer::FromCompressed(SharedBuffer(std::move(Payload)), VerifyRawHash, VerifyRawSize);
+			CHECK(CompressedBlob);
+			CHECK(VerifyRawHash == RawHash);
+			IoBuffer Decompressed = CompressedBlob.Decompress().AsIoBuffer();
+			CHECK(IoHash::HashBuffer(Decompressed) == RawHash);
+		}
+	}
+}
+
+namespace blockstore::testing {
+	IoBuffer MakeMetaData(const IoHash& BlobHash, const std::vector<std::pair<std::string, std::string>>& KeyValues)
+	{
+		CbObjectWriter Writer;
+		Writer.AddHash("rawHash"sv, BlobHash);
+		Writer.BeginObject("values");
+		{
+			for (const auto& V : KeyValues)
+			{
+				Writer.AddString(V.first, V.second);
+			}
+		}
+		Writer.EndObject();	 // values
+		return Writer.Save().GetBuffer().AsIoBuffer();
+	};
+
+}  // namespace blockstore::testing
+
+TEST_CASE("BuildStore.Metadata")
+{
+	using namespace blockstore::testing;
+
+	ScopedTemporaryDirectory _;
+
+	BuildStoreConfig Config;
+	Config.RootDirectory = _.Path() / "build_store";
+
+	std::vector<IoHash>	  BlobHashes;
+	std::vector<IoBuffer> MetaPayloads;
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+
+		for (size_t I = 0; I < 5; I++)
+		{
+			BlobHashes.push_back(IoHash::HashBuffer(&I, sizeof(I)));
+			MetaPayloads.push_back(MakeMetaData(BlobHashes.back(), {{"index", fmt::format("{}", I)}}));
+			MetaPayloads.back().SetContentType(ZenContentType::kCbObject);
+		}
+		Store.PutMetadatas(BlobHashes, MetaPayloads);
+
+		std::vector<IoBuffer> ValidateMetaPayloads = Store.GetMetadatas(BlobHashes, nullptr);
+		CHECK(ValidateMetaPayloads.size() == MetaPayloads.size());
+		for (size_t I = 0; I < ValidateMetaPayloads.size(); I++)
+		{
+			const IoHash ExpectedHash = IoHash::HashBuffer(MetaPayloads[I]);
+			CHECK_EQ(IoHash::HashBuffer(ValidateMetaPayloads[I]), ExpectedHash);
+		}
+	}
+	{
+		GcManager			  Gc;
+		BuildStore			  Store(Config, Gc);
+		std::vector<IoBuffer> ValidateMetaPayloads = Store.GetMetadatas(BlobHashes, nullptr);
+		CHECK(ValidateMetaPayloads.size() == MetaPayloads.size());
+		for (size_t I = 0; I < ValidateMetaPayloads.size(); I++)
+		{
+			const IoHash ExpectedHash = IoHash::HashBuffer(MetaPayloads[I]);
+			CHECK_EQ(IoHash::HashBuffer(ValidateMetaPayloads[I]), ExpectedHash);
+		}
+		for (const IoHash& BlobHash : BlobHashes)
+		{
+			CHECK(!Store.GetBlob(BlobHash));
+		}
+	}
+	std::vector<IoHash> CompressedBlobsHashes;
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+		for (size_t I = 0; I < 5; I++)
+		{
+			IoBuffer		 Blob			= CreateSemiRandomBlob(4711 + I * 7);
+			CompressedBuffer CompressedBlob = CompressedBuffer::Compress(SharedBuffer(std::move(Blob)));
+			CompressedBlobsHashes.push_back(CompressedBlob.DecodeRawHash());
+			IoBuffer Payload = std::move(CompressedBlob).GetCompressed().Flatten().AsIoBuffer();
+			Payload.SetContentType(ZenContentType::kCompressedBinary);
+
+			Store.PutBlob(CompressedBlobsHashes.back(), Payload);
+		}
+		std::vector<IoBuffer> MetadataPayloads = Store.GetMetadatas(CompressedBlobsHashes, nullptr);
+		for (const auto& MetadataIt : MetadataPayloads)
+		{
+			CHECK(!MetadataIt);
+		}
+		for (const IoHash& BlobHash : CompressedBlobsHashes)
+		{
+			IoBuffer Blob = Store.GetBlob(BlobHash);
+			CHECK(Blob);
+			IoBuffer DecompressedBlob = CompressedBuffer::FromCompressedNoValidate(std::move(Blob)).Decompress().AsIoBuffer();
+			CHECK(DecompressedBlob);
+			CHECK_EQ(IoHash::HashBuffer(DecompressedBlob), BlobHash);
+		}
+	}
+
+	std::vector<IoBuffer> BlobMetaPayloads;
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+		for (const IoHash& BlobHash : CompressedBlobsHashes)
+		{
+			BlobMetaPayloads.push_back(MakeMetaData(BlobHash, {{"blobHash", fmt::format("{}", BlobHash)}}));
+			BlobMetaPayloads.back().SetContentType(ZenContentType::kCbObject);
+		}
+		Store.PutMetadatas(CompressedBlobsHashes, BlobMetaPayloads);
+
+		std::vector<IoBuffer> MetadataPayloads = Store.GetMetadatas(CompressedBlobsHashes, nullptr);
+		CHECK(MetadataPayloads.size() == BlobMetaPayloads.size());
+		for (size_t I = 0; I < MetadataPayloads.size(); I++)
+		{
+			const IoBuffer& MetadataPayload = MetadataPayloads[I];
+			CHECK_EQ(IoHash::HashBuffer(MetadataPayload), IoHash::HashBuffer(BlobMetaPayloads[I]));
+		}
+	}
+
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+
+		std::vector<IoBuffer> MetadataPayloads = Store.GetMetadatas(CompressedBlobsHashes, nullptr);
+		CHECK(MetadataPayloads.size() == BlobMetaPayloads.size());
+		for (size_t I = 0; I < MetadataPayloads.size(); I++)
+		{
+			const IoBuffer& MetadataPayload = MetadataPayloads[I];
+			CHECK(IoHash::HashBuffer(MetadataPayload) == IoHash::HashBuffer(BlobMetaPayloads[I]));
+		}
+		for (const IoHash& BlobHash : CompressedBlobsHashes)
+		{
+			IoBuffer Blob = Store.GetBlob(BlobHash);
+			CHECK(Blob);
+			IoBuffer DecompressedBlob = CompressedBuffer::FromCompressedNoValidate(std::move(Blob)).Decompress().AsIoBuffer();
+			CHECK(DecompressedBlob);
+			CHECK_EQ(IoHash::HashBuffer(DecompressedBlob), BlobHash);
+		}
+
+		BlobMetaPayloads.clear();
+		for (const IoHash& BlobHash : CompressedBlobsHashes)
+		{
+			BlobMetaPayloads.push_back(
+				MakeMetaData(BlobHash, {{"blobHash", fmt::format("{}", BlobHash)}, {"replaced", fmt::format("{}", true)}}));
+			BlobMetaPayloads.back().SetContentType(ZenContentType::kCbObject);
+		}
+		Store.PutMetadatas(CompressedBlobsHashes, BlobMetaPayloads);
+	}
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+
+		std::vector<IoBuffer> MetadataPayloads = Store.GetMetadatas(CompressedBlobsHashes, nullptr);
+		CHECK(MetadataPayloads.size() == BlobMetaPayloads.size());
+		for (size_t I = 0; I < MetadataPayloads.size(); I++)
+		{
+			const IoBuffer& MetadataPayload = MetadataPayloads[I];
+			CHECK(IoHash::HashBuffer(MetadataPayload) == IoHash::HashBuffer(BlobMetaPayloads[I]));
+		}
+		for (const IoHash& BlobHash : CompressedBlobsHashes)
+		{
+			IoBuffer Blob = Store.GetBlob(BlobHash);
+			CHECK(Blob);
+			IoBuffer DecompressedBlob = CompressedBuffer::FromCompressedNoValidate(std::move(Blob)).Decompress().AsIoBuffer();
+			CHECK(DecompressedBlob);
+			CHECK_EQ(IoHash::HashBuffer(DecompressedBlob), BlobHash);
+		}
+	}
+}
+
+TEST_CASE("BuildStore.GC")
+{
+	using namespace blockstore::testing;
+
+	ScopedTemporaryDirectory _;
+
+	BuildStoreConfig Config;
+	Config.RootDirectory = _.Path() / "build_store";
+
+	std::vector<IoHash>	  CompressedBlobsHashes;
+	std::vector<IoBuffer> BlobMetaPayloads;
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+		for (size_t I = 0; I < 5; I++)
+		{
+			IoBuffer		 Blob			= CreateSemiRandomBlob(4711 + I * 7);
+			CompressedBuffer CompressedBlob = CompressedBuffer::Compress(SharedBuffer(std::move(Blob)));
+			CompressedBlobsHashes.push_back(CompressedBlob.DecodeRawHash());
+			IoBuffer Payload = std::move(CompressedBlob).GetCompressed().Flatten().AsIoBuffer();
+			Payload.SetContentType(ZenContentType::kCompressedBinary);
+
+			Store.PutBlob(CompressedBlobsHashes.back(), Payload);
+		}
+		for (const IoHash& BlobHash : CompressedBlobsHashes)
+		{
+			BlobMetaPayloads.push_back(MakeMetaData(BlobHash, {{"blobHash", fmt::format("{}", BlobHash)}}));
+			BlobMetaPayloads.back().SetContentType(ZenContentType::kCbObject);
+		}
+		Store.PutMetadatas(CompressedBlobsHashes, BlobMetaPayloads);
+	}
+	{
+		GcManager  Gc;
+		BuildStore Store(Config, Gc);
+
+		{
+			GcResult Result = Gc.CollectGarbage(GcSettings{.BuildStoreExpireTime = GcClock::Now() - std::chrono::hours(1),
+														   .CollectSmallObjects	 = false,
+														   .IsDeleteMode		 = false,
+														   .Verbose				 = true});
+			CHECK(!Result.WasCancelled);
+			for (const IoHash& BlobHash : CompressedBlobsHashes)
+			{
+				IoBuffer Blob = Store.GetBlob(BlobHash);
+				CHECK(Blob);
+				IoBuffer DecompressedBlob = CompressedBuffer::FromCompressedNoValidate(std::move(Blob)).Decompress().AsIoBuffer();
+				CHECK(DecompressedBlob);
+				CHECK(IoHash::HashBuffer(DecompressedBlob) == BlobHash);
+			}
+
+			std::vector<IoBuffer> MetadataPayloads = Store.GetMetadatas(CompressedBlobsHashes, nullptr);
+			CHECK(MetadataPayloads.size() == BlobMetaPayloads.size());
+			for (size_t I = 0; I < MetadataPayloads.size(); I++)
+			{
+				const IoBuffer& MetadataPayload = MetadataPayloads[I];
+				CHECK(IoHash::HashBuffer(MetadataPayload) == IoHash::HashBuffer(BlobMetaPayloads[I]));
+			}
+		}
+		{
+			GcResult Result = Gc.CollectGarbage(GcSettings{.BuildStoreExpireTime = GcClock::Now() + std::chrono::hours(1),
+														   .CollectSmallObjects	 = true,
+														   .IsDeleteMode		 = true,
+														   .Verbose				 = true});
+			CHECK(!Result.WasCancelled);
+			for (const IoHash& BlobHash : CompressedBlobsHashes)
+			{
+				IoBuffer Blob = Store.GetBlob(BlobHash);
+				CHECK(!Blob);
+			}
+
+			std::vector<IoBuffer> MetadataPayloads = Store.GetMetadatas(CompressedBlobsHashes, nullptr);
+			CHECK(MetadataPayloads.size() == BlobMetaPayloads.size());
+			for (size_t I = 0; I < MetadataPayloads.size(); I++)
+			{
+				const IoBuffer& MetadataPayload = MetadataPayloads[I];
+				CHECK(!MetadataPayload);
+			}
+		}
+	}
+}
+
+void
+buildstore_forcelink()
+{
+}
+
+#endif
+
+}  // namespace zen
diff --git a/src/zenstore/compactcas.cpp b/src/zenstore/compactcas.cpp
index 2be0542db..b64bc26dd 100644
--- a/src/zenstore/compactcas.cpp
+++ b/src/zenstore/compactcas.cpp
@@ -226,7 +226,7 @@ CasContainerStrategy::InsertChunk(IoBuffer Chunk, const IoHash& ChunkHash)
 }
 
 std::vector<CasStore::InsertResult>
-CasContainerStrategy::InsertChunks(std::span<IoBuffer> Chunks, std::span<IoHash> ChunkHashes)
+CasContainerStrategy::InsertChunks(std::span<const IoBuffer> Chunks, std::span<const IoHash> ChunkHashes)
 {
 	ZEN_MEMSCOPE(GetCasContainerTag());
 
@@ -323,7 +323,7 @@ CasContainerStrategy::FilterChunks(HashKeySet& InOutChunks)
 }
 
 bool
-CasContainerStrategy::IterateChunks(std::span<IoHash>												  ChunkHashes,
+CasContainerStrategy::IterateChunks(std::span<const IoHash>											  ChunkHashes,
 									const std::function<bool(size_t Index, const IoBuffer& Payload)>& AsyncCallback,
 									WorkerThreadPool*												  OptionalWorkerPool,
 									uint64_t														  LargeSizeLimit)
diff --git a/src/zenstore/compactcas.h b/src/zenstore/compactcas.h
index 07e620086..2eb4c233a 100644
--- a/src/zenstore/compactcas.h
+++ b/src/zenstore/compactcas.h
@@ -52,11 +52,11 @@ struct CasContainerStrategy final : public GcStorage, public GcReferenceStore
 	~CasContainerStrategy();
 
 	CasStore::InsertResult				InsertChunk(IoBuffer Chunk, const IoHash& ChunkHash);
-	std::vector<CasStore::InsertResult> InsertChunks(std::span<IoBuffer> Chunks, std::span<IoHash> ChunkHashes);
+	std::vector<CasStore::InsertResult> InsertChunks(std::span<const IoBuffer> Chunks, std::span<const IoHash> ChunkHashes);
 	IoBuffer							FindChunk(const IoHash& ChunkHash);
 	bool								HaveChunk(const IoHash& ChunkHash);
 	void								FilterChunks(HashKeySet& InOutChunks);
-	bool								IterateChunks(std::span<IoHash>													ChunkHashes,
+	bool								IterateChunks(std::span<const IoHash>											ChunkHashes,
 													  const std::function<bool(size_t Index, const IoBuffer& Payload)>& AsyncCallback,
 													  WorkerThreadPool*													OptionalWorkerPool,
 													  uint64_t															LargeSizeLimit);
diff --git a/src/zenstore/gc.cpp b/src/zenstore/gc.cpp
index 7ac10d613..fe5ae284b 100644
--- a/src/zenstore/gc.cpp
+++ b/src/zenstore/gc.cpp
@@ -1081,7 +1081,7 @@ GcManager::CollectGarbage(const GcSettings& Settings)
 						ZEN_INFO("GCV2: Locking state for {} reference checkers", ReferenceCheckers.size());
 						{
 							ZEN_TRACE_CPU("GcV2::LockReferencers");
-							// From this point we have blocked all writes to all References (DiskBucket/ProjectStore) until
+							// From this point we have blocked all writes to all References (DiskBucket/ProjectStore/BuildStore) until
 							// we delete the ReferenceLockers
 							Latch WorkLeft(1);
 							{
@@ -1108,7 +1108,7 @@ GcManager::CollectGarbage(const GcSettings& Settings)
 							ZEN_TRACE_CPU("GcV2::UpdateLockedState");
 
 							// Locking all references checkers so we have a steady state of which references are used
-							// From this point we have blocked all writes to all References (DiskBucket/ProjectStore) until
+							// From this point we have blocked all writes to all References (DiskBucket/ProjectStore/BuildStore) until
 							// we delete the ReferenceCheckers
 							Latch WorkLeft(1);
 
@@ -1739,6 +1739,7 @@ GcScheduler::AppendGCLog(std::string_view Id, GcClock::TimePoint StartTime, cons
 				{
 					Writer << "CacheExpireTime"sv << ToDateTime(Settings.CacheExpireTime);
 					Writer << "ProjectStoreExpireTime"sv << ToDateTime(Settings.ProjectStoreExpireTime);
+					Writer << "BuildStoreExpireTime"sv << ToDateTime(Settings.BuildStoreExpireTime);
 					Writer << "CollectSmallObjects"sv << Settings.CollectSmallObjects;
 					Writer << "IsDeleteMode"sv << Settings.IsDeleteMode;
 					Writer << "SkipCidDelete"sv << Settings.SkipCidDelete;
@@ -1940,6 +1941,7 @@ GcScheduler::SchedulerThread()
 			std::chrono::seconds LightweightGcInterval			   = m_Config.LightweightInterval;
 			std::chrono::seconds MaxCacheDuration				   = m_Config.MaxCacheDuration;
 			std::chrono::seconds MaxProjectStoreDuration		   = m_Config.MaxProjectStoreDuration;
+			std::chrono::seconds MaxBuildStoreDuration			   = m_Config.MaxBuildStoreDuration;
 			uint64_t			 DiskSizeSoftLimit				   = m_Config.DiskSizeSoftLimit;
 			bool				 SkipCid						   = false;
 			GcVersion			 UseGCVersion					   = m_Config.UseGCVersion;
@@ -1975,6 +1977,10 @@ GcScheduler::SchedulerThread()
 				{
 					MaxProjectStoreDuration = TriggerParams.MaxProjectStoreDuration;
 				}
+				if (TriggerParams.MaxBuildStoreDuration != std::chrono::seconds::max())
+				{
+					MaxBuildStoreDuration = TriggerParams.MaxBuildStoreDuration;
+				}
 				if (TriggerParams.DiskSizeSoftLimit != 0)
 				{
 					DiskSizeSoftLimit = TriggerParams.DiskSizeSoftLimit;
@@ -2046,6 +2052,8 @@ GcScheduler::SchedulerThread()
 				MaxCacheDuration == GcClock::Duration::max() ? GcClock::TimePoint::min() : Now - MaxCacheDuration;
 			GcClock::TimePoint ProjectStoreExpireTime =
 				MaxProjectStoreDuration == GcClock::Duration::max() ? GcClock::TimePoint::min() : Now - MaxProjectStoreDuration;
+			GcClock::TimePoint BuildStoreExpireTime =
+				MaxBuildStoreDuration == GcClock::Duration::max() ? GcClock::TimePoint::min() : Now - MaxBuildStoreDuration;
 
 			const GcStorageSize TotalSize = m_GcManager.TotalStorageSize();
 
@@ -2102,6 +2110,10 @@ GcScheduler::SchedulerThread()
 					{
 						ProjectStoreExpireTime = SizeBasedExpireTime;
 					}
+					if (SizeBasedExpireTime > BuildStoreExpireTime)
+					{
+						BuildStoreExpireTime = SizeBasedExpireTime;
+					}
 				}
 
 				std::chrono::seconds RemainingTimeUntilGc =
@@ -2227,6 +2239,7 @@ GcScheduler::SchedulerThread()
 
 			bool GcSuccess = CollectGarbage(CacheExpireTime,
 											ProjectStoreExpireTime,
+											BuildStoreExpireTime,
 											DoDelete,
 											CollectSmallObjects,
 											SkipCid,
@@ -2333,6 +2346,7 @@ GcScheduler::ScrubStorage(bool DoDelete, bool SkipCid, std::chrono::seconds Time
 bool
 GcScheduler::CollectGarbage(const GcClock::TimePoint& CacheExpireTime,
 							const GcClock::TimePoint& ProjectStoreExpireTime,
+							const GcClock::TimePoint& BuildStoreExpireTime,
 							bool					  Delete,
 							bool					  CollectSmallObjects,
 							bool					  SkipCid,
@@ -2416,6 +2430,7 @@ GcScheduler::CollectGarbage(const GcClock::TimePoint& CacheExpireTime,
 
 						const GcSettings Settings = {.CacheExpireTime					= CacheExpireTime,
 													 .ProjectStoreExpireTime			= ProjectStoreExpireTime,
+													 .BuildStoreExpireTime				= BuildStoreExpireTime,
 													 .CollectSmallObjects				= CollectSmallObjects,
 													 .IsDeleteMode						= Delete,
 													 .SkipCidDelete						= SkipCid,
@@ -2447,6 +2462,7 @@ GcScheduler::CollectGarbage(const GcClock::TimePoint& CacheExpireTime,
 							}
 							SB.Append(fmt::format("      Cache cutoff time:           {}\n", Settings.CacheExpireTime));
 							SB.Append(fmt::format("      Project store cutoff time:   {}\n", Settings.ProjectStoreExpireTime));
+							SB.Append(fmt::format("      Build store cutoff time:     {}\n", Settings.BuildStoreExpireTime));
 						};
 
 						{
@@ -2552,6 +2568,7 @@ GcScheduler::CollectGarbage(const GcClock::TimePoint& CacheExpireTime,
 				if (Delete)
 				{
 					GcClock::TimePoint KeepRangeStart = Min(CacheExpireTime, ProjectStoreExpireTime);
+					KeepRangeStart					  = Min(KeepRangeStart, BuildStoreExpireTime);
 					m_LastGcExpireTime				  = KeepRangeStart;
 					std::unique_lock Lock(m_GcMutex);
 					m_DiskUsageWindow.KeepRange(KeepRangeStart.time_since_epoch().count(), GcClock::Duration::max().count());
diff --git a/src/zenstore/include/zenstore/accesstime.h b/src/zenstore/include/zenstore/accesstime.h
new file mode 100644
index 000000000..a28dc908b
--- /dev/null
+++ b/src/zenstore/include/zenstore/accesstime.h
@@ -0,0 +1,47 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include <zenstore/gc.h>
+
+#include <gsl/gsl-lite.hpp>
+
+namespace zen {
+
+// This store the access time as seconds since epoch internally in a 32-bit value giving is a range of 136 years since epoch
+struct AccessTime
+{
+	explicit AccessTime(GcClock::Tick Tick) noexcept : SecondsSinceEpoch(ToSeconds(Tick)) {}
+	AccessTime& operator=(GcClock::Tick Tick) noexcept
+	{
+		SecondsSinceEpoch.store(ToSeconds(Tick), std::memory_order_relaxed);
+		return *this;
+	}
+	operator GcClock::Tick() const noexcept
+	{
+		return std::chrono::duration_cast<GcClock::Duration>(std::chrono::seconds(SecondsSinceEpoch.load(std::memory_order_relaxed)))
+			.count();
+	}
+
+	AccessTime(AccessTime&& Rhs) noexcept : SecondsSinceEpoch(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed)) {}
+	AccessTime(const AccessTime& Rhs) noexcept : SecondsSinceEpoch(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed)) {}
+	AccessTime& operator=(AccessTime&& Rhs) noexcept
+	{
+		SecondsSinceEpoch.store(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed), std::memory_order_relaxed);
+		return *this;
+	}
+	AccessTime& operator=(const AccessTime& Rhs) noexcept
+	{
+		SecondsSinceEpoch.store(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed), std::memory_order_relaxed);
+		return *this;
+	}
+
+private:
+	static uint32_t ToSeconds(GcClock::Tick Tick)
+	{
+		return gsl::narrow<uint32_t>(std::chrono::duration_cast<std::chrono::seconds>(GcClock::Duration(Tick)).count());
+	}
+	std::atomic_uint32_t SecondsSinceEpoch;
+};
+
+}  // namespace zen
diff --git a/src/zenstore/include/zenstore/blockstore.h b/src/zenstore/include/zenstore/blockstore.h
index 97357e5cb..0c72a13aa 100644
--- a/src/zenstore/include/zenstore/blockstore.h
+++ b/src/zenstore/include/zenstore/blockstore.h
@@ -156,7 +156,7 @@ public:
 	void WriteChunk(const void* Data, uint64_t Size, uint32_t Alignment, const WriteChunkCallback& Callback);
 
 	typedef std::function<void(std::span<BlockStoreLocation> Locations)> WriteChunksCallback;
-	void WriteChunks(std::span<IoBuffer> Datas, uint32_t Alignment, const WriteChunksCallback& Callback);
+	void WriteChunks(std::span<const IoBuffer> Datas, uint32_t Alignment, const WriteChunksCallback& Callback);
 
 	IoBuffer TryGetChunk(const BlockStoreLocation& Location) const;
 	void	 Flush(bool ForceNewBlock);
diff --git a/src/zenstore/include/zenstore/buildstore/buildstore.h b/src/zenstore/include/zenstore/buildstore/buildstore.h
new file mode 100644
index 000000000..302af5f9c
--- /dev/null
+++ b/src/zenstore/include/zenstore/buildstore/buildstore.h
@@ -0,0 +1,186 @@
+
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zenstore/blockstore.h>
+
+#include <zencore/iohash.h>
+#include <zenstore/accesstime.h>
+#include <zenstore/caslog.h>
+#include <zenstore/gc.h>
+#include "../compactcas.h"
+#include "../filecas.h"
+
+ZEN_THIRD_PARTY_INCLUDES_START
+#include <tsl/robin_map.h>
+ZEN_THIRD_PARTY_INCLUDES_END
+
+namespace zen {
+
+struct BuildStoreConfig
+{
+	std::filesystem::path RootDirectory;
+	uint32_t			  SmallBlobBlockStoreMaxBlockSize	   = 256 * 1024 * 1024;
+	uint64_t			  SmallBlobBlockStoreMaxBlockEmbedSize = 1 * 1024 * 1024;
+	uint32_t			  SmallBlobBlockStoreAlignement		   = 16;
+	uint32_t			  MetadataBlockStoreMaxBlockSize	   = 64 * 1024 * 1024;
+	uint32_t			  MetadataBlockStoreAlignement		   = 8;
+};
+
+class BuildStore : public GcReferencer, public GcReferenceLocker  //, public GcStorage
+{
+public:
+	explicit BuildStore(const BuildStoreConfig& Config, GcManager& Gc);
+	virtual ~BuildStore();
+
+	void	 PutBlob(const IoHash& BlobHashes, const IoBuffer& Payload);
+	IoBuffer GetBlob(const IoHash& BlobHashes);
+
+	struct BlobExistsResult
+	{
+		bool HasBody	 = 0;
+		bool HasMetadata = 0;
+	};
+
+	std::vector<BlobExistsResult> BlobsExists(std::span<const IoHash> BlobHashes);
+
+	void				  PutMetadatas(std::span<const IoHash> BlobHashes, std::span<const IoBuffer> MetaDatas);
+	std::vector<IoBuffer> GetMetadatas(std::span<const IoHash> BlobHashes, WorkerThreadPool* OptionalWorkerPool);
+
+	void Flush();
+
+private:
+	void CompactState();
+
+	uint64_t ReadPayloadLog(const RwLock::ExclusiveLockScope&, const std::filesystem::path& LogPath, uint64_t SkipEntryCount);
+	uint64_t ReadMetadataLog(const RwLock::ExclusiveLockScope&, const std::filesystem::path& LogPath, uint64_t SkipEntryCount);
+
+	//////// GcReferencer
+	virtual std::string						   GetGcName(GcCtx& Ctx) override;
+	virtual GcStoreCompactor*				   RemoveExpiredData(GcCtx& Ctx, GcStats& Stats) override;
+	virtual std::vector<GcReferenceChecker*>   CreateReferenceCheckers(GcCtx& Ctx) override;
+	virtual std::vector<GcReferenceValidator*> CreateReferenceValidators(GcCtx& Ctx) override;
+
+	//////// GcReferenceLocker
+	virtual std::vector<RwLock::SharedLockScope> LockState(GcCtx& Ctx) override;
+
+#pragma pack(push)
+#pragma pack(1)
+	struct PayloadEntry
+	{
+		static const uint8_t kTombStone	 = 0x10u;  // Represents a deleted key/value
+		static const uint8_t kStandalone = 0x20u;  // This payload is stored as a standalone value
+
+		uint8_t Flags	  = 0;
+		uint8_t Reserved1 = 0;
+		uint8_t Reserved2 = 0;
+		uint8_t Reserved3 = 0;
+	};
+	static_assert(sizeof(PayloadEntry) == 4);
+
+	struct PayloadDiskEntry
+	{
+		PayloadEntry Entry;		// 4 bytes
+		IoHash		 BlobHash;	// 20 bytes
+	};
+	static_assert(sizeof(PayloadDiskEntry) == 24);
+
+	struct MetadataEntry
+	{
+		BlockStoreLocation Location;  // 12 bytes
+
+		ZenContentType		 ContentType = ZenContentType::kCOUNT;	// 1 byte
+		static const uint8_t kTombStone	 = 0x10u;					// Represents a deleted key/value
+		uint8_t				 Flags		 = 0;						// 1 byte
+
+		uint8_t Reserved1 = 0;
+		uint8_t Reserved2 = 0;
+	};
+	static_assert(sizeof(MetadataEntry) == 16);
+
+	struct MetadataDiskEntry
+	{
+		MetadataEntry Entry;	 // 16 bytes
+		IoHash		  BlobHash;	 // 20 bytes
+		uint8_t		  Reserved1 = 0;
+		uint8_t		  Reserved2 = 0;
+		uint8_t		  Reserved3 = 0;
+		uint8_t		  Reserved4 = 0;
+	};
+	static_assert(sizeof(MetadataDiskEntry) == 40);
+
+#pragma pack(pop)
+
+	static bool ValidatePayloadDiskEntry(const PayloadDiskEntry& Entry, std::string& OutReason);
+	static bool ValidateMetadataDiskEntry(const MetadataDiskEntry& Entry, std::string& OutReason);
+
+	struct PayloadIndex
+	{
+		uint32_t Index = std::numeric_limits<uint32_t>::max();
+
+		operator bool() const { return Index != std::numeric_limits<uint32_t>::max(); };
+		PayloadIndex() = default;
+		explicit PayloadIndex(size_t InIndex) : Index(uint32_t(InIndex)) {}
+					operator size_t() const { return Index; };
+		inline auto operator<=>(const PayloadIndex& Other) const = default;
+	};
+
+	struct MetadataIndex
+	{
+		uint32_t Index = std::numeric_limits<uint32_t>::max();
+
+		operator bool() const { return Index != std::numeric_limits<uint32_t>::max(); };
+		MetadataIndex() = default;
+		explicit MetadataIndex(size_t InIndex) : Index(uint32_t(InIndex)) {}
+					operator size_t() const { return Index; };
+		inline auto operator<=>(const MetadataIndex& Other) const = default;
+	};
+
+	struct BlobIndex
+	{
+		uint32_t Index = std::numeric_limits<uint32_t>::max();
+
+		operator bool() const { return Index != std::numeric_limits<uint32_t>::max(); };
+		BlobIndex() = default;
+		explicit BlobIndex(size_t InIndex) : Index(uint32_t(InIndex)) {}
+					operator size_t() const { return Index; };
+		inline auto operator<=>(const BlobIndex& Other) const = default;
+	};
+
+	struct BlobEntry
+	{
+		PayloadIndex  Payload;
+		MetadataIndex Metadata;
+		AccessTime	  LastAccessTime;
+	};
+	static_assert(sizeof(BlobEntry) == 12);
+
+	const BuildStoreConfig m_Config;
+	GcManager&			   m_Gc;
+
+	RwLock m_Lock;
+
+	std::vector<PayloadEntry>  m_PayloadEntries;
+	std::vector<MetadataEntry> m_MetadataEntries;
+
+	std::vector<BlobEntry>							  m_BlobEntries;
+	tsl::robin_map<IoHash, BlobIndex, IoHash::Hasher> m_BlobLookup;
+
+	FileCasStrategy		 m_LargeBlobStore;
+	CasContainerStrategy m_SmallBlobStore;
+	BlockStore			 m_MetadataBlockStore;
+
+	TCasLogFile<PayloadDiskEntry>  m_PayloadlogFile;
+	TCasLogFile<MetadataDiskEntry> m_MetadatalogFile;
+	uint64_t					   m_BlobLogFlushPosition = 0;
+	uint64_t					   m_MetaLogFlushPosition = 0;
+
+	std::unique_ptr<HashSet> m_TrackedCacheKeys;
+
+	friend class BuildStoreGcReferenceChecker;
+	friend class BuildStoreGcReferencePruner;
+	friend class BuildStoreGcCompator;
+};
+
+void buildstore_forcelink();
+
+}  // namespace zen
diff --git a/src/zenstore/include/zenstore/cache/cachedisklayer.h b/src/zenstore/include/zenstore/cache/cachedisklayer.h
index 05400c784..5a51718d3 100644
--- a/src/zenstore/include/zenstore/cache/cachedisklayer.h
+++ b/src/zenstore/include/zenstore/cache/cachedisklayer.h
@@ -5,6 +5,7 @@
 #include "cacheshared.h"
 
 #include <zencore/stats.h>
+#include <zenstore/accesstime.h>
 #include <zenstore/blockstore.h>
 #include <zenstore/caslog.h>
 
diff --git a/src/zenstore/include/zenstore/cache/cacheshared.h b/src/zenstore/include/zenstore/cache/cacheshared.h
index 521c78bb1..ef1b803de 100644
--- a/src/zenstore/include/zenstore/cache/cacheshared.h
+++ b/src/zenstore/include/zenstore/cache/cacheshared.h
@@ -72,42 +72,4 @@ struct CacheContentStats
 bool IsKnownBadBucketName(std::string_view BucketName);
 bool ValidateIoBuffer(ZenContentType ContentType, IoBuffer Buffer);
 
-//////////////////////////////////////////////////////////////////////////
-
-// This store the access time as seconds since epoch internally in a 32-bit value giving is a range of 136 years since epoch
-struct AccessTime
-{
-	explicit AccessTime(GcClock::Tick Tick) noexcept : SecondsSinceEpoch(ToSeconds(Tick)) {}
-	AccessTime& operator=(GcClock::Tick Tick) noexcept
-	{
-		SecondsSinceEpoch.store(ToSeconds(Tick), std::memory_order_relaxed);
-		return *this;
-	}
-	operator GcClock::Tick() const noexcept
-	{
-		return std::chrono::duration_cast<GcClock::Duration>(std::chrono::seconds(SecondsSinceEpoch.load(std::memory_order_relaxed)))
-			.count();
-	}
-
-	AccessTime(AccessTime&& Rhs) noexcept : SecondsSinceEpoch(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed)) {}
-	AccessTime(const AccessTime& Rhs) noexcept : SecondsSinceEpoch(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed)) {}
-	AccessTime& operator=(AccessTime&& Rhs) noexcept
-	{
-		SecondsSinceEpoch.store(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed), std::memory_order_relaxed);
-		return *this;
-	}
-	AccessTime& operator=(const AccessTime& Rhs) noexcept
-	{
-		SecondsSinceEpoch.store(Rhs.SecondsSinceEpoch.load(std::memory_order_relaxed), std::memory_order_relaxed);
-		return *this;
-	}
-
-private:
-	static uint32_t ToSeconds(GcClock::Tick Tick)
-	{
-		return gsl::narrow<uint32_t>(std::chrono::duration_cast<std::chrono::seconds>(GcClock::Duration(Tick)).count());
-	}
-	std::atomic_uint32_t SecondsSinceEpoch;
-};
-
 }  // namespace zen
diff --git a/src/zenstore/include/zenstore/gc.h b/src/zenstore/include/zenstore/gc.h
index 3daae0a93..67aadef71 100644
--- a/src/zenstore/include/zenstore/gc.h
+++ b/src/zenstore/include/zenstore/gc.h
@@ -55,6 +55,7 @@ struct GcSettings
 {
 	GcClock::TimePoint CacheExpireTime		  = GcClock::Now();
 	GcClock::TimePoint ProjectStoreExpireTime = GcClock::Now();
+	GcClock::TimePoint BuildStoreExpireTime	  = GcClock::Now();
 	bool			   CollectSmallObjects	  = false;
 	bool			   IsDeleteMode			  = false;
 	bool			   SkipCidDelete		  = false;
@@ -412,6 +413,7 @@ struct GcSchedulerConfig
 	std::chrono::seconds  Interval{};
 	std::chrono::seconds  MaxCacheDuration{86400};
 	std::chrono::seconds  MaxProjectStoreDuration{604800};
+	std::chrono::seconds  MaxBuildStoreDuration{604800};
 	bool				  CollectSmallObjects				= true;
 	bool				  Enabled							= true;
 	uint64_t			  DiskReserveSize					= 1ul << 28;
@@ -496,6 +498,7 @@ public:
 		bool					 CollectSmallObjects	 = false;
 		std::chrono::seconds	 MaxCacheDuration		 = std::chrono::seconds::max();
 		std::chrono::seconds	 MaxProjectStoreDuration = std::chrono::seconds::max();
+		std::chrono::seconds	 MaxBuildStoreDuration	 = std::chrono::seconds::max();
 		uint64_t				 DiskSizeSoftLimit		 = 0;
 		bool					 SkipCid				 = false;
 		bool					 SkipDelete				 = false;
@@ -528,6 +531,7 @@ private:
 	void		 SchedulerThread();
 	bool		 CollectGarbage(const GcClock::TimePoint& CacheExpireTime,
 								const GcClock::TimePoint& ProjectStoreExpireTime,
+								const GcClock::TimePoint& BuildStoreExpireTime,
 								bool					  Delete,
 								bool					  CollectSmallObjects,
 								bool					  SkipCid,