If the goal is solely Docker images with a standard size in the 20-40MB range, this can be achieved without additional tooling. After switching our development and deployment flow to docker, my team quickly tired of the 200-400MB images that seemed to be accepted as commonplace. We started basing our containers on alpine (essentially, busybox with a package manager) or alpine derivatives, and dropped into that target size immediately. Spinning up 8-10 microservices locally for a full frontend development stack is a shockingly better experience when that involves a 200MB download rather than a 2GB one.
This is in no way a negative commentary on Nix; it looks like an interesting solution to a well-known problem.
This is in no way a negative commentary on Nix; it looks like an interesting solution to a well-known problem.