[8organicbits]

Looks like cache.nixos.org may be a long term archive (never evicts artifacts) so that is suitable for long-term reproducible builds for nixos things.

If I'm following correctly, this would prevent issues like builds failing due to the leftpad package getting unpublished, since you'd use the cache/archive instead of failing to fetch the missing package.

> and you've lost (or pruned) your store

It's common for academic code, for example, to be built once, published and then shelved. The "you" in "your store" ends up being different people over time.

Apt generally has this issue too, while Debian keeps old packages around (snapshot archive), third parties origins and other apt based systems may not.

I'm going to explore nix more, thank you!

[tripleo1]

maybe not if you want to build from source and the oriiginal tgz/git goes offline?