Comment by jonotime

Author here.

The idea with nix flakes is it has a lock file which should guarantee the same build. This is like package-lock.json or pdm.lock which contains dependency checksums for every package.

Docker works more like your standard package manager. If you ask for mysql 5, today you may get mysql 5.1, but next week you may get mysql 5.2. So it does not come with a guarantee.