Kubernetes isn't building the image, really, it's just passing the Nix expression directly to the container runtime that Nix would provide. This is more or less

Kubernetes isn't building the image, really, it's just passing the Nix expression directly to the container runtime that Nix would provide. This is more or less how Nix works already, as the Nix tooling takes Nix expressions and builds derivations which are stored in the Nix store.