With 5 consumers and 10 partitions, how many partitions per consumer and is any consumer idle?

• A. Two partitions per consumer; none idle
• B. One partition per consumer; some idle
• C. All partitions are shared; some duplication
• D. Five partitions per consumer; all active

Answer: (A)

Partitions in a topic are the units of parallelism, and in a consumer group each partition is assigned to exactly one consumer at a time. The total of 10 partitions is divided among the 5 consumers, and because 10 is evenly divisible by 5, each consumer gets two partitions. That means every consumer has work to do, so none are idle. If the numbers weren’t divisible (or if there were more consumers than partitions), some consumers could end up idle or unevenly loaded.