A stream processing application is consuming from a topic with five partitions.

In Kafka Streams,the number of stream tasks = number of input partitions × num.stream.threads × number of instances,but only as many as the number of partitions can actively consume at once.

However, in this case,Kafka Streams assigns one task per partition, and because there are 5 partitions and 15 threads (3 instances × 5 threads),15 tasks are created, andall 15 can be activedepending on processing topology.

FromKafka Streams Developer Guide:

"Kafka Streams creates one task per input partition. If you increase the number of stream threads, it runs multiple tasks in parallel within a single instance."

So,15 stream tasks will be created and 15 will be actively consuming.