We are running internal DNS caching resolvers and query forwards for efficiency, security, and dynamic scaling.
There are three (3) DNS nodes (dns-0[1-3].inf.prd.gitlab.net) that are running the PowerDNS Recursor software. These nodes are configured to do lookups from the root DNS servers and cache the results for the allowable cacheable timeframe.
The DNS servers are chef managed through the gitlab_dns cookbook
and applied via the infra-base-dns role.