Retry Topics and Dead Letters

A warehouse service reads label-requests, a topic with 6 partitions, and calls an external shipping provider to create a label for each shipment. Requests arrive at 30 a second, which is 5 a second for each partition. Each call normally takes about 200 ms.

Suppose one call times out. The service is written to retry in place: it waits up to 5 seconds for each attempt, makes 5 attempts, and pauses 1, 2, 4, and 8 seconds between them. That one shipment holds its partition for up to 25 seconds of attempts plus 15 seconds of pauses, which is 40 seconds