There are multiple multiples :) both (hidden) primary and secondaries are multiple, snapshots every 20 minutes and forward-update functionality from the secondaries with replicated tsig over powerdns api every 120 seconds. since they are static they only need to replicate once.

if you register a zone and open the snippets quickly, there is a green notification saying tsig replication underway for x amount of seconds and until that happens RFC 2136 updates are not possible but the ones that use api are available right off the bat.