github-workflows-caching-strategies

Caching accelerates Rust CI by storing dependencies and build artifacts between workflow runs. Use rust-cache or sccache to automatically cache cargo build outputs, reducing rebuild time from minutes to seconds on subsequent runs.

The best strategy depends on your workflow. rust-cache handles cargo dependencies and artifacts automatically; sccache compiles incrementally across runs; manual caching with cache keys offers fine-grained control. Choose based on build complexity and cache hit frequency.

Yes. rust-cache and sccache serve different purposes and can complement each other. rust-cache manages cargo state; sccache optimizes compiler caching. Combined, they maximize cache efficiency and reduce overall build times.

Cache keys determine whether a stored cache is reused. Multi-key strategies—combining Cargo.lock, OS, and Rust version—ensure cache hits when dependencies haven't changed while invalidating when they have, balancing storage and rebuild efficiency.

Cache the cargo registry index, downloaded dependencies, and compiled build artifacts (target directory). Avoid caching unstable or platform-specific outputs. Focus on high-cost, stable artifacts to maximize hit rate and minimize cache size.

Low cache hit rates stem from poor cache keys, frequent dependency changes, or caching the wrong paths. Verify your cache key includes stable identifiers like Cargo.lock, ensure target directory inclusion, and check for workflow changes invalidating previous caches.