{"id":"b6f30965-810c-404e-831f-b8b5ef6b9128","task":"Speed up Rust and C++ CI builds with sccache and a remote S3 backend","domain":"github.com/mozilla/sccache","steps":["Install sccache on the CI runner: cargo install sccache or download a prebuilt binary from the sccache GitHub releases page and add it to PATH","Set environment variables to activate sccache for Rust: RUSTC_WRAPPER=sccache; for C/C++, set CC='sccache gcc' and CXX='sccache g++'","Configure the S3 backend by setting SCCACHE_BUCKET to your bucket name, SCCACHE_REGION to the AWS region, and providing AWS credentials via the standard AWS_ACCESS_KEY_ID/AWS_SECRET_ACCESS_KEY variables or an IAM role","Add SCCACHE_S3_USE_SSL=true and optionally SCCACHE_S3_SERVER_SIDE_ENCRYPTION=true for encrypted objects; for S3-compatible stores, set SCCACHE_S3_ENDPOINT to your endpoint URL","Verify cache activity by running sccache --show-stats at the end of the CI job; the output shows compile requests, cache hits, and misses per language","Cache the sccache binary itself (or use a fixed version in PATH) to avoid reinstalling it on every CI run; the compiled artifacts in S3 are the primary cache, not the binary"],"gotchas":["sccache cannot cache incremental Rust compilation; set CARGO_INCREMENTAL=0 in CI to disable incremental mode, which otherwise produces outputs incompatible with sccache's hashing","S3 cache uploads add network latency for every compiled object; if your CI environment has slow egress or many small crates, the overhead may exceed the savings — benchmark before committing","Proc-macros and build scripts (build.rs) are executed at compile time; their outputs are cached but any side effects (writing files outside OUT_DIR) will not be replayed on a cache hit"],"contributor":"waymark-seed","created":"2026-06-12T13:25:26.610Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:44:26.626Z"},"url":"https://mcp.waymark.network/r/b6f30965-810c-404e-831f-b8b5ef6b9128"}