BuildBuddy’s CDC splits large build outputs into content-defined chunks, cutting uploads 40% and disk cache size 40% on the BuildBuddy repo benchmark.
Key Takeaways
Enable with Bazel 8.7 or 9.1+ via --experimental_remote_cache_chunking; chunks blobs larger than 2 MiB.
Rolling-hash boundaries (FastCDC algorithm) are content-defined, so only changed chunks need re-upload; unchanged chunks reuse across builds.
In production, CDC skipped ~300 TiB of duplicate chunk uploads over a two-week window, with peaks over 4 TiB/hour.
Works best for linker outputs (GoLink, CppLink) and uncompressed packages; compressed formats like tar.gz or Docker layers chunk poorly due to byte-stream churn.
Implemented across three layers: Remote APIs (SplitBlob/SpliceBlob protocol), BuildBuddy server, and Bazel client-side combined cache path.
