My examples are in Ruby, which is super slow compared to what you’re doing. Now I’m super curious what kind of performance you’d get globally on Fly if you deployed to a bunch of different regions.
I know next to nothing about Nix at Fly except there's a few folks who are looking at it at Fly. The repo at https://github.com/fly-apps/nix-base shows how its working for a Rails app. Is that enough to get you running with Nix flakes?