[poly2it]

What if you set up a sandbox pool? Maybe I'm rambling, I haven't read much Nix source code, but that should allow for only a couple of milliseconds of latency on these types of builds. I have considered forking Nix to make this work, but in my testing with my experimental build system, I never experienced much latency in builds. The trick to reduce latency in development builds is to forcibly disable the network lookups which normally happen before Nix starts building a derivation:

    preferLocalBuild = true;
    allowSubstitutes = false;

Set these in each derivation. The most impactful thing you could do in a Nix fork according to my testing in this case is to build derivations preemptively while you are fetching substitutes and caches simultaneously, instead of doing it in order.

If you are interested in seeing my experiment, it's open on your favourite forge:

https://github.com/poly2it/kein