StatefulSets for Databases and Queues

A Deployment treats pods as interchangeable. A StatefulSet gives each pod a stable name (db-0, db-1), ordered startup, and its own volume.

apiVersion: v1
kind: Service
metadata: { name: db }
spec:
  clusterIP: None            # headless service gives each pod a DNS name
  selector: { app: db }
  ports: [{ port: 5432 }]
---
apiVersion: apps/v1
kind: StatefulSet
metadata: { name: db }
spec:
  serviceName: db
  replicas: 3
  selector: { matchLabels: { app: db } }
  template:
    metadata: { labels: { app: db } }
    spec:
      containers:
        - name: postgres
          image: postgres:14
          volumeMounts: [{ name: data, mountPath: /var/lib/postgresql/data }]
  volumeClaimTemplates:
    - metadata: { name: data }
      spec:
        accessModes: [ReadWriteOnce]
        resources: { requests: { storage: 20Gi } }

Pods get names like db-0.db.default.svc. Deleting the StatefulSet does not delete the volumes. Running databases on Kubernetes needs replication, backups and tested failover; for many teams a managed database such as RDS is the safer choice.