...

public class StreamsBuilder {
  @Deprecate
  public synchronized Topology build();
}

Proposed Changes

In order to leverage the new configuration, users will need to call StreamsBuilder#build(Properties) instead of StreamsBuilder#build(). This is an already established pattern that users need to follow to enable topology optimization. As we predict that we might need to access the config in the DSL more often in the future, we also propose to deprecate StreamsBuilder#build() method to lift the mental burden for users to know which of both methods that should use.

All stateful operators (like aggregate(), reduce(),  count(), or join(), will use either the RocksDB or in-memory store depending on the configuration. Of course, if the store is overwritten for an individual operator via Materialized the operator overwrite will be used. The improved Materialized interface allows to switch the store type more easily without the need to specify a store name.

...