Nix Best Practices

This one covers the practical patterns you actually need when setting up Nix flakes: proper use of follows to avoid downloading nixpkgs multiple times, how to apply overlays correctly, and handling unfree packages without fighting the tooling. The binary overlay pattern is especially useful if you're dealing with open-core tools where the nixpkgs version is missing features. It also walks through dev shell configurations with native dependencies and environment variables, plus the common gotchas like why config.allowUnfree doesn't work with nix develop. Good reference if you're past the hello world stage but still hitting walls with flake architecture decisions.