MIGRATING A CRITICAL KUBERNETES DEPLOYMENT FROM THE DEFAULT NAMESPACE WITHOUT ANY DOWNTIME

Summary from the TLDR DevOps newsletter

A Kubernetes engineer describes how to move a service out of the default namespace without downtime, using an ExternalName service as a DNS-level forwarding address. The approach lets dozens of dependent services keep calling the old cluster-internal DNS name while traffic silently routes to the new deployment, with no code changes required from other teams. A temporary policy exception handled the ingress side, allowing both the old and new ingress rules to coexist briefly while traffic was confirmed on the new deployment before the old one was removed.