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This is an asymmetric non-window join. The basic semantics is a KTable lookup for each KStream record (while each KTable input record updates the current KTable view but does never yield any result record). The result is a KStream. Pay attention, that the KTable lookup is done on the current KTable state, and thus, out-of-order records can yield non-deterministic result. Furthermore, in practice Kafka Streams does not guarantee that all records will be processed in timestamp order (even if processing records in timestamp order is the goal, it is only best effort). The table below shows the output (for each processed input record) for both offered join variants. Pay attention, that some input records do not produce output records.

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