It's a pity, DNS handles negative lookup caching / TTLs (in fact that is exactly what the TTL field in DNS zones are!). So negative lookups can be cached, but y

It's a pity, DNS handles negative lookup caching / TTLs (in fact that is exactly what the TTL field in DNS zones are!). So negative lookups can be cached, but you need to do thinking about it ahead of time and set sensible TTLs (preferably configurable) for those negative caches.