The core trade-off
Kubernetes offers three workload controllers. Deployments handle stateless apps with interchangeable pods and rolling updates. StatefulSets manage stateful workloads with stable identities and persistent storage. DaemonSets run one pod per node. The decision matters most for databases.
Deployments work for 80% of production clusters, according to 2024 CNCF data. They scale fast, update cleanly, and don't care which pod serves traffic. Web servers, APIs, batch jobs: stateless by design.
StatefulSets handle the other 25% (some clusters run both). Each pod gets a persistent identity, ordered creation, and its own PersistentVolumeClaim via volumeClaimTemplates. PostgreSQL, MongoDB, Kafka: they need stable network IDs and durable storage. Delete a StatefulSet pod and it comes back with the same hostname and data.
Where teams stumble
The temptation is to hack Deployments with manual PVCs. It's possible but clunky. You lose ordered scaling, stable DNS, and coordinated updates. One banking CTO told us they tried this approach in 2023 and spent six months debugging data corruption issues before migrating to StatefulSets.
StatefulSets scale slower and complicate rolling updates. They're not faster, they're correct. For stateful workloads, that trade-off matters.
Configuration reality
Define volumeClaimTemplates in your StatefulSet spec. Each pod gets its own claim. Storage class matters: local-path for dev, iSCSI or NFS for production. Size it based on growth projections, not current usage. Resizing PVCs mid-flight is painful.
ReadinessProbe controls traffic routing. LivenessProbe triggers restarts. InitContainers handle pre-start setup like schema migrations. Multi-container pods work for sidecars: logging agents, backup tools, monitoring exporters.
The operator question
Database operators (like those from Crunchy Data or Percona) abstract StatefulSet complexity. They're worth evaluating if you're running multiple clusters or need automated failover. But understand what they're doing under the hood first.
The decision tree: stateless workload equals Deployment. Stateful workload with ordered scaling and persistent identity equals StatefulSet. Everything else is edge cases.
Kubernetes adoption hit $4.5B in enterprise spend by 2025, with stateful workloads growing 40% year-over-year. The question isn't whether to use StatefulSets. It's whether your team understands when.