docker build vs BuildKit: Faster Image Builds in CI
BuildKit is the modern build backend for Docker - it parallelizes stages, supports cache mounts and build secrets, and is now the default.
The legacy docker build executes a Dockerfile sequentially with coarse layer caching. BuildKit (exposed via docker buildx and now the default builder) parallelizes independent stages, adds cache mounts, build secrets, and richer cache export/import - a major CI speedup with the same Dockerfile.
| docker build (legacy) | BuildKit | |
|---|---|---|
| Stage parallelism | Sequential | Parallel |
| Cache mounts | No | Yes (--mount=type=cache) |
| Build secrets | Workarounds | Native (--secret) |
| Cache export/import | Limited | Rich (registry, gha, local) |
| Status | Legacy | Default builder |
In CI
BuildKit is the clear choice in modern pipelines: parallel stages cut wall-clock time, cache mounts keep package downloads warm across builds, and the gha or registry cache backends let one job reuse another job's layers. Legacy docker build still exists for old setups but leaves speed on the table. Enable BuildKit (it is on by default in recent Docker) or use docker buildx.
Speed it up
Export the BuildKit cache to a registry or the GitHub Actions cache and import it on the next run for warm layers. Builds still run on CI runners; faster managed runners shorten the actual layer build.
The verdict
Use BuildKit (buildx) - it is the default, builds in parallel, and adds cache mounts and secrets. There is little reason to stay on legacy docker build except for very old, frozen environments.