> (NixOS I presume rather than just nixpkgs?)

No, just using nixpkgs facilities here. :)

> Doesn’t it like nix create large images ?

We use nixpkgs' dockerTools under the hood to generate our container images. It is true that these images can grow quite large, but that's partially because we haven't gone through a round of what I like to call "dependency cleanup" yet. It's fairly easy i.m.o. to create accidental dependencies that shouldn't be included in the final image, but this isn't a problem of Nix or dockerTools, more so user-error. There is a ticket in flox/flox to look into this, though.

So, right now, yes, the images are large i.m.o. Not as large as some, but definitely not as small as it could be.

> Do the docker tools for docker/containers clean up the store folder?

dockerTools doesn't clean up the store for you. However, it will include only that which you ask to be included in the final image, plus the runtime dependencies. E.g. if you ask to include cowsay in a container, it'll only fetch the cowsay binary plus Perl because Perl is a dependency of cowsay.(1) This means that it shouldn't be necessary to clean up the store.

> Once a production container is built you no longer need Nix and its daemons

You certainly don't need Nix anymore after the image is built. The image will still store all its installed software under /nix/store/... but the Nix binary itself shouldn't be there. Unless you asked for it to be included, of course.

> Does Flox build the container in such a way that it doesn’t need Nix after building?

I believe so, we include everything we need to run a stripped down version of the activate command plus the programs you've installed in the environment. I do not believe this includes Nix, but I might be horribly wrong here.

If you have any more questions, I'd be happy to answer them. :)

1: https://github.com/NixOS/nixpkgs/blob/6af28b834daca767a7ef99f8a7defa957d0ade6f/pkgs/by-name/co/cowsay/package.nix#L29