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Kafka Streams has a defined "contract" about timestamp propagation at the Processor API level: all processors within a sub-topology, see the timestamp from the input topic record that is currently processed and this timestamp will be used for all result records when writing them to a topic, too. For punctuation, the used output record timestamp is the current event-time or wall-clock time (depending on the punctuation type) that triggers the punctuation (i.e., for event-time the timestamp of last processed record that fires the punctuation).

For the DSL and also for custom operators, it would be desirable to allow timestamp manipulation at Processor API level for individual records that are forwarded. This allows to support a larger scope of possible semantics for stream processing.

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