Split-Brain DNS Is What Actually Breaks Multi-Cloud — And How to Design Around It

Most multi-cloud designs start with the network diagram: VPCs, transit hubs, private interconnects, routing tables. DNS gets one small box in the corner, labelled "DNS", and that is usually where the trouble starts — not during the design review, but three months later, at 2 a.m., when the same hostname returns three different answers depending on which cloud you ask from.

1. The symptom: one name, several truths

The classic failure looks like this. api.internal.example.com resolves to a private address in AWS because Route 53 has a private hosted zone attached to that VPC. In Azure, the same name falls through to public DNS and returns the public load balancer — or NXDOMAIN, because Private DNS zones are linked per virtual network and one link was never added after a new subscription was created.…