Docker BuildKit and Advanced Build Features

The original Docker build engine processed a Dockerfile strictly top to bottom, one instruction at a time, with a simple linear cache. That worked but was slow and limited: independent stages could not build in parallel, there was no clean way to cache a package manager's download directory between builds, and secrets needed during a build leaked into image layers. BuildKit is the modern build engine — now the default — that re-architects building around a dependency graph, enabling parallelism, smarter caching, build-time secrets and mounts, and multi-platform images. The payoff is dramatically faster, more secure builds with the same Dockerfile. Understanding BuildKit's features is what lets you turn a two-minute build into a ten-second one and stop baking credentials into images, which matters enormously when builds run on every push in CI.