I had a couple of blogs from cloudflare regarding DNS infrastructure. One is regarding DNS secondary and the other about having multiple DNS primary servers in a different provider.
Regarding the Secondary DNS is interesting how they have moved to a kubernetes infrastructure with its issues.
For setting up, different primary servers in a different provider makes sense nowadays with so many options. But there is some research to be done. You dont want the new primary DNS servers relaying in the same cloud provider as your current setup. It is interesting the mention using OctoDNS for zone management and TeamCity for CI/CD.