Hi,
as I said, I have direct contact with PowerDNS through work and can ask them about it.
The next thing I would have is not directly related to performance, but the powerDNS recursor does not follow cnames in its default config.
Only with the setting of
followupFunction = “followCNAMERecords” – this makes PowerDNS lookup your CNAME
it resolves the cnames to the end.
I’ll write to Peter from PowerDNS tomorrow and ask him about ZonetoCache and followCNAMERecords.