The first time a cluster leaked traffic across projects, it was a quiet disaster. Two teams, two apps, one shared ingress — and a slow bleed of requests from one domain into another. Logs showed nothing suspicious, but the architecture had gaps. The root cause was simple: no domain-based resource separation in Kubernetes Ingress.
Kubernetes Ingress is powerful, but by default it does not enforce strict isolation between applications hosted in the same cluster. Without precise domain-based routing rules and namespaces aligned with ingress configuration, requests can slip into services they were never meant to reach. The fix is not guesswork; it’s architecture.
Domain-based resource separation means mapping each domain to its own ingress definition, namespace, and backend services. This ensures requests for api.team1.example.com cannot touch workloads for api.team2.example.com. The separation should be enforced at the ingress controller level, with TLS certificates scoped tightly to each domain. This makes cross-project leaks impossible unless misconfigurations are introduced intentionally.
The best practice is to define one ingress per domain, avoid wildcard hosts that span multiple environments, and pair ingress rules with network policies. Use role-based access control to make sure no team can deploy or edit ingress resources outside their namespace. Terminate TLS at the ingress controller with certificates per host, and ensure your DNS points only to dedicated endpoints for that ingress.