Nice! Also narinfo-cache-negative-ttl should be set to zero.
That makes sense if you know that the hash could appear in the cache but if it will never appear and cannot ever appear that we are needlessly asking the binary cache way more often.
Usually you’re building things, so either it’s in the cache or you build it. There’s no need to constantly recheck hashes. Nix caches this in-memory anyway so in the scope of
nix invocation it will be cached anyway.