Himani Arora shows how to join two Kafka streams together:
KStream-KStream Join
It is a sliding window join, that means, all tuples close to each other with regard to time are joined. Time here is the difference up to size of the window.
These joins are always windowed joins because otherwise, the size of the internal state store used to perform the join would grow indefinitely.
In the following example, we perform an inner join between two streams. The output the joined stream will be of type
KStream<K, ...>
Read on to learn more about two additional join types.