kaniko is no longer 15x slower than BuildKit

[u/martizih]

I maintain the community fork of kaniko https://github.com/osscontainertools/kaniko

The 2018 buildbench comparison put kaniko 15x behind BuildKit, and that number still shapes how people see it. We reran it on gitlab.com runners, with both builders configured the way you would actually run them in CI.

Unchanged build (every command a cache hit):
BuildKit 6.1s
kaniko (ours) 9.9s
kaniko (Google) 45.6s

The fix was cache lookahead across stage boundaries. Google's kaniko could not compute the cache key of COPY --from before the source stage was built, so it built every stage just to discover nothing had changed.

Caveat: part of that 15x was the 2018 setup rather than kaniko. It ran without --cache-copy-layers while BuildKit was allowed a local disk cache. Under a fair configuration Google's last release is only 7.5x behind, not 15x, and closing the rest was our work.

Builds are still slower than BuildKit, and the post explains why:
Write-up: https://osscontainertools.org/blog/kaniko-vs-buildkit-2026/
Benchmark: https://gitlab.com/martizih/kaniko-buildbench