I'm a Rust newbie, and one of the things that I've found frustrating is that the default docker build experience is extremely slow. As it downloads crates, then dependencies, then finally my app - I often get distracted, start doing something else, then come back several minutes later and forget what I was doing

Recently, I had the idea to make it a little better by combining multistage builds with some of the amazing features from BuildKit. Specifically, cache mounts, which let a build container cache directories for compilers & package managers. Here's a quick annotated before & after from a real app I encountered.

This is a standard enough multistage Dockerfile. Nothing seemingly terrible or great here - just a normal build stage, and a smaller runtime stage.