How do services in different namespaces communicate in Kubernetes?

All services in a Kubernetes cluster are reachable via DNS using the Fully Qualified Domain Name (FQDN):

<service-name>.<namespace>.svc.cluster.local

For example, a service named postgres in the production namespace is reachable at postgres.production.svc.cluster.local from any pod in any namespace. If NetworkPolicies are in place, you must explicitly allow cross-namespace traffic.