The nodes of a topology are grouped into sub-topologies if they are connected. In contrast, two sub-topologies are not connected but can be linked to each other via topics, i.e., if one sub-topology writes into a topic and another sub-topology reads from the same topic. Message ProcessorContext.forward(Record, String) forwards} using custom Processors and Transformers are not considered in the topology graph.

When KafkaStreams.start() is called, different sub-topologies will be constructed and executed as independent tasks.