The last time I saw DNS throughput or performance issues was around 2003 on a network with 200K desktops and servers. That was 17 years ago, and they don't have a problem any more, despite growing in footprint to nearly half a million client machines.

I struggle to understand how DNS can possibly be a performance issue in 2020. In most corporate environments, the "working set" of a typical DNS servers will fit in the L3 cache of the CPU, or even the L2 cache.

The amount of network traffic involved is similarly miniscule. If all 200K of your client machines sent 100 requests per second, each 100 bytes in size, all of those to just one server, that adds up to a paltry 2 Gbps.

If your DNS servers are struggling with that, get better servers. Or networks. Or IT engineers.