Tvix store in production

Replit.com is website used by millions of users to collaboratively create software with their teammates and now with Replit’s AI Agent. Replit uses Nix to manage the underlying development environments. When building a Nix environment, downloading files from cache.nixos.org can take a long time, and many files would be duplicated across Repls. In this talk, I will show how Replit uses Nix local-overlay-stores to manage Nix caching, as well as our new cache disk architecture using tvix-store.