Only if it's not already in your cache or in /etc/hosts

You can put hosts file on RAM disk.

With some servers it's also possible to save and reload caches.

Assuming you're not doing hundreds of thousands of new lookups (sites you've never visited before) every day, it's very easy to configure a system for yourself that is faster than any open resolver.

There is one trade-off: if sites switch IP's without telling their users (preferring instead to wait for ttl's in open caches to expire) then for those sites that like to hop from IP to another unexpectedly, you need to monitor for this. This is rare though, and you can try to safeguard against it by "pinging" less oft visited sites periodically, but it does happen occasionally.