StatefulSets: Ordered, Stateful Workload Management

You're designing the Kubernetes deployment for a new PostgreSQL database. Do you reach for a Deployment or a StatefulSet? The answer determines whether your data survives Pod restarts, whether replicas can reliably find each other, and whether you wake up to a broken cluster after a node failure.

This is the fundamental question that separates stateless from stateful workloads. Deployments are built for stateless applications — web servers, API backends, batch processors — where any Pod can handle any request and losing a Pod means nothing more than rescheduling a replacement. StatefulSets exist for a different world: databases, message queues, caching clusters where each replica has identity, owns specific data, and must be discoverable by stable network names.