BuildKit: Docker's Hidden Gem That Can Build Almost Anything

BuildKit, the engine behind docker build, is actually a general-purpose build framework that can produce any artifact describable as filesystem operations. Its architecture uses LLB (Low-Level Build definition) as an intermediate representation, pluggable frontends for custom build languages, and content-addressable caching. The article demonstrates building a custom frontend that reads YAML specs to produce Alpine APK packages, showing how BuildKit can handle non-Docker use cases.