This Kafka Streams example shows how to use a state store where old keys are eventually expired (or pruned).

The way this is done is by using a WindowStore instead of a KeyValueStore.

As you'll see in the example, this requires using the WindowStore functionality in a bit of a specialized way because WindowStore is designed to store different values for a given key based on what window the value was updated in.

To run this example, first run MyProducer then run MyKafkaStreams.

If you'd like to perform a second run with a fresh start, use a different MyProducer.INPUT_TOPIC, use a different APPLICATION_ID_CONFIG in MyKafkaStreams, and delete /tmp/state-store-pruner-state.