The Nix Binary Cache and AWS (nixcon2025)

Behind the Scenes of cache.nixos.org: Scaling Nix’s Binary Cache to Infinity The Nix binary cache is the silent powerhouse of the Nix ecosystem: every day, it fields thousands of requests per second—amounting to nearly 6 billion requests per month!—for NixOS and Nix users worldwide. But what makes it work at scale, how—or why—is its simplicity a virtue, and how does an ongoing partnership between AWS and the Nix Foundation ensure its availability for years to come? In this fireside chat, join Ron (Flox), Tarus (AWS), Tom Bereknyei and moderator Ross (Flox) for a conversation about: - What the Nix binary cache actually is… - …and why it matters for the community, reproducibility, and even the survival of historical software; - How AWS came to support cache.nixos.org - Why the binary cache’s “dumb” design is a feature, not a bug; - What goes in the cache? - Challenges and lessons learned: scaling, cost optimization, and keeping things simple - Why this partnership is important for the Nix ecosystem Whether you’re a builder, a Nix maintainer, a user, or just curious about how open source infra runs at global scale, this conversation will offer insights, anecdotes, and a look at how communities and clouds can support each other. about this event: https://talks.nixcon.org/nixcon-2025/talk/QXZJ9H/