How would you do this in a generic, reusable way company-wide for any Dockerfile? Given that you don't know the targets beforehand, the names, or even the number of stages.

It is of course possible to do for a single project with a bit of effort: build each stage with a remote OCI cache source, push the cash there after. But... that sucks.

What you want is the `max` cache type in buildkit[1]. Except... not much supports that yet. The native S3 cache would also be good once it stabalizes.

1. https://github.com/moby/buildkit#export-cache

If you're running the CI inside AWS, and assuming the code isn't doing anything stupid, it will be fast enough for nobody to notice.

the cache is small but if you have a `docker buildx build --cache-from --push` type command it will always pull the image at the end and try to push it again (although it'll get layer already exists responses), for ~250mb images on gitlab I find this do-nothing job takes about 2.5 mins in total (vs a 10 min build if the entire cache were to be invalidated by a new base image version). I'd very much like it if I could say "if the entire build was cached don't bother pulling it at the end", maybe buildkit is the tool for that job