Clicking around from your link you get to https://doc.powerdns.com/recursor/index.html https://doc.powerdns.com/recursor/index.html > A quad Xeon 3GHz has been

Clicking around from your link you get to https://doc.powerdns.com/recursor/index.html https://doc.powerdns.com/recursor/index.html > A quad Xeon 3GHz has been measured functioning very well at 400000 real life replayed packets per second. So that's more like 40 servers. Realistically the complexity of serving DNS is probably somewhere between Fortunes and Json Serialization in the Techempower benchmarks: https://www.techempower.com/benchmarks/#section=data-r21&test=fortune https://www.techempower.com/benchmarks/#section=data-r21&tes... So it's possible you could do it with 10, far less than you'd want for proper redundancy.