> But I feel like there's still room for a "magic" /nix/store that skips the copying and decompression stage altogether— something that works using standard nix invocations (like Magic Nix Cache), but presents itself as a Kubernetes Volume, so that in cases where a path already exists on-node, the existing files (in the cache pod) are simply mounted/served directly into whatever container ran a nix command.

Mostly a digression since it's not Nix, but I've wondered a bit about this sort of thing when building AUR packages on Arch Linux. The very last step of the builder is to compress the package, which in the vast majority of my uses is followed immediately by installing it, which of course decompresses the package. I've wondered why there isn't some (non-default) option to say "I don't need to keep the package itself around; just install it as soon as its built". I'm sure for my specific use case there's a simpler solution, but I've always wondered if there's a hacky way to get around things more generally by making a tool that can mimic the expected compression API but then creates a "fake" compressed artifact that no-ops (or maybe puts in a valid header followed by non-compressed data) and then injects that implementation into the PATH. You'd be able to invoke it with something like `fakecompress --zstd makepkg -si`, and it would invoke `makepkg -si` with the no-op zstd implementation.