StatefulSets vs Deployments in Kubernetes.

StatefulSets are designed for stateful applications requiring unique, persistent identities and stable storage. Deployments are for stateless apps.

Pods in a Deployment are interchangeable and have random names. Pods in a StatefulSet have sticky, ordered identities (pod-0, pod-1). They are created sequentially. If pod-1 crashes, it is reborn as pod-1 attached to the exact same PersistentVolume. This is mandatory for databases or clustering software.