This announcement relates to an internal architecture change.
After some weird issues that we were unable to satisfactorily resolve with our BIND 9.5 based caching resolver pool, we've decided to migrate our resolvers to the PowerDNS Recursor.
The issue we observed with BIND was that it was failing to consistently return fully formed responses to some zones from a small subset of authoritative name servers. Upon further examination we realized that we could see the full response using 'dig', however the responses cached by BIND were inconsistent and missing portions (most notably MX records) that were present in the 'dig' results. Debugging output led us to believe BIND was timing out, however, we were unable to discern why. PowerDNS Recursor did not exhibit the same timeout or incomplete response issues and its cached responses matched the results from 'dig' in every case we examined. Additionally, PowerDNS Recursor is able to return initial results much quicker than BIND.
We've used PowerDNS Recursor in the past, but we switched to BIND (believing it to be "good enough") after discovering an issue that would cause pdns_recursor to use all available memory over time. This issue has been fixed for a long time, but there was no pressing reason to revert until now.
We do not anticipate any negative operational impact from these changes. Contact technical support if you have any questions regarding this change.