Comment by hamandcheese

We do exactly this at my dayjob - we have (multiple) very specific combinations of (erlang, elixir, hex, rebar3) that we use which are pinned to exactly the versions we need. We have a private Nix cache so we only have to build them once.

https://www.cachix.org/ simplifies running a custom cache. Well worth the money, IMO.

That said, learning nix and setting up a nix cache is still a lot of work. Docker buildx might offer you some more knobs to cache portions of your build in a finer-grained manner without having to take the nix plunge.