Caching in Docker - the hardest thing in computer science

The document discusses challenges with caching dependencies and sources when building Docker images across different environments. It finds that builds are faster when caching locally but slower when caching dependencies across CI/CD pipelines due to differences in file permissions and generated files. Specifically: 1) File permissions differ between local builds and CI/CD due to user and group settings 2) Generated files like documentation and cache files cause issues because they are not ignored 3) Reinstalling all dependencies from scratch on each build is slow. It provides solutions like fixing group permissions, setting dockerignore, pre-building wheels, and multi-stage builds to better leverage caching across environments.