Which description best matches KStream-to-KTable join characteristics?

Which description best matches KStream-to-KTable join characteristics?

• A. Output: KTable; Non-windowed; Yes; Key Or Foreign-Key Based
• B. Output: KStream; Windowed; Yes; Key Based
• C. Output: KStream; Non-windowed; Yes; Key Based
• D. Output: KStream; Non-windowed; No; Key Based

Answer: (C)

When you join a KStream with a KTable, each incoming stream record is enriched using the current value from the KTable for the same key, and a new stream record is emitted downstream. This makes the output a KStream, not a KTable, because the stream of enriched results is what flows out. There’s no time window applied to this operation, so it is non-windowed. The join relies on the KTable’s stored state to look up the corresponding value, which makes the join stateful. Finally, the lookup and enrichment are performed using the stream’s key, so it’s keyed by that same key, not based on a foreign key. So the best description is: Output is a KStream; Non-windowed; Yes (stateful); Key Based.

When you join a KStream with a KTable, each incoming stream record is enriched using the current value from the KTable for the same key, and a new stream record is emitted downstream. This makes the output a KStream, not a KTable, because the stream of enriched results is what flows out. There’s no time window applied to this operation, so it is non-windowed. The join relies on the KTable’s stored state to look up the corresponding value, which makes the join stateful. Finally, the lookup and enrichment are performed using the stream’s key, so it’s keyed by that same key, not based on a foreign key. So the best description is: Output is a KStream; Non-windowed; Yes (stateful); Key Based.