There's an optimzation I'm aware of where nix will de-duplicate individual files with hard links. This wouldn't be safe in almost any other context, but is safe

There's an optimzation I'm aware of where nix will de-duplicate individual files with hard links. This wouldn't be safe in almost any other context, but is safe with nix because the files are immutable. So you have have 100 variations of libcurl and only "pay" for the unique files.