What kache actually caches
Summary
Kunobi explains kache, a content-addressed Rust build cache that speeds up cross-worktree and CI builds by caching the dependencies and toolchain rather than individual compiled outputs. The post covers how kache integrates as a RUSTC_WRAPPER, how cache keys are computed from source, dependencies, and toolchain, and how hits are restored via reflinks or hardlinks. It also discusses remote caching with S3-compatible backends, workspace build locks, and monitoring tools like kache monitor, stats, and doctor.