May 2026 Summaries

BuildBuddy's Remote Cache utilizes Content-Defined Chunking (CDC) to incrementally handle large build outputs by moving only the changed bytes rather than entire files. This approach significantly reduces data transfer and storage by reusing previously seen chunks when a binary, bundle, package, or archive remains mostly unchanged. Implemented in Bazel versions 8.7 and 9.1+, CDC allows for efficient remote caching by splitting files into content-based chunks, ensuring that only new or altered chunks are uploaded. This innovation addresses the traditional inefficiencies of whole-blob caching, particularly in actions that involve linking, bundling, or packaging, where small source changes can lead to large output variations. The technique has shown substantial savings in network and storage resources, with BuildBuddy reporting up to 85% deduplication of written bytes, translating to significant reductions in data uploads and cache size. By treating large-file outputs as a generic problem and applying CDC, BuildBuddy enhances the effectiveness of remote caching, allowing for better cache retention and faster builds without altering the underlying actions.