Exactly-Once & Streaming SQL — Week 3 CheckWeek 3 of Stream Processing: delivery guarantees earned across chains, and SQL as the streaming interface.

"Exactly-once processing" in a checkpointed stream processor actually means:

End-to-end exactly-once into an external sink requires the sink to be either:

Uber's ad pipeline layers Kafka transactions AND record-UUID idempotency AND Pinot upserts. Why isn't one mechanism enough?

Streaming SQL (FlinkSQL, ksqlDB) democratizes stream processing. The governance tradeoff production teams hit:

A streaming join of two streams must hold state. What bounds it?

Kafka Streams' exactly-once guarantee ends at Kafka's boundary. The moment your processor calls an external REST API per event, that call is: