What is the difference between Deployment and StatefulSet in Kubernetes?

The main difference between Deployment and StatefulSet in Kubernetes is how they manage the lifecycle of pods and their state.

• Deployment is designed for managing stateless applications. It provides scaling, updates, and rollbacks by creating and deleting pods without preserving unique identity or persistent state. Pods in Deployment are interchangeable.

• StatefulSet is used for stateful applications, where each pod's unique identity, stable network identifiers, and persistent storage are important. StatefulSet guarantees the order of creation, deletion, and scaling of pods, and maintains their names and attachment to PersistentVolumes.

Example usage:

• Deployment — web servers, stateless APIs.
• StatefulSet — databases, cache services, where data integrity and uniqueness of instances are crucial.

Thus, the choice depends on the application's requirements for state and identity.