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2 stories

Banner: Docker multi-stage build cache only storing the final stage in CI

DevOps & CI/CD Bug Report

Docker Buildx cache barely helps multi-stage builds in CI: cache mode=min

Ryan Pham · Jun 4, 2025 · 6 min read

We enabled BuildKit's GitHub Actions cache and our multi-stage Go build still took 9 minutes on every run. The default cache export mode only stores layers of the final image, not the builder stage where all the time is spent. mode=max and per-branch scopes cut it to 2 minutes.

Banner: Docker image layers where an early COPY instruction invalidates every layer below it

DevOps & CI/CD Bug Report

Docker build reinstalls every dependency on each commit: COPY order and cache busting

Daniel Tran · Oct 15, 2024 · 8 min read

Every push to our FastAPI service spent seven minutes reinstalling the same Python packages. COPY . . ran before pip install, and a missing .dockerignore let .git changes bust the cache. Reordering layers and a cache mount cut builds to 50 seconds.