My own domain is hosted on two completely separate providers, with my own DNS server acting as a hidden master, with DNSSEC signing to minimize the possibility of shenanigans. I can have any number of replicas on any number of networks.
The issue comes when you have to depend on a single service. When you're using traffic management from NS1 or content delivery from CloudFlare, then you have no choice but to use a single DNS provider. Unless they have some special service for whoever pays enough.
The issue comes when you have to depend on a single service. When you're using traffic management from NS1 or content delivery from CloudFlare, then you have no choice but to use a single DNS provider. Unless they have some special service for whoever pays enough.