There's an interesting conversation going on on the #NANOG #mailinglist. It's about running a #DNS resolver for a medium-sized service provider network:

Recommended DNS server for a medium 20-30k users isp

I particularly love that the people from @quad9dns chipped in, and revealed how they split their front- and backend with #dnsdist. Splitting the front- and backend of internet-facing services is something that I already learned in University as a best-practice.