Per thread how many consumers are allowed, and can the consumer be multi-threaded?

Per thread how many consumers are allowed, and can the consumer be multi-threaded?

• A. One; Not multi-threaded
• B. Two; Multi-threaded
• C. One; Multi-threaded
• D. Unlimited; Not allowed

Answer: (A)

A Kafka consumer is not thread-safe, so one thread should own a single consumer instance and use it in that thread only. If you need parallelism, run multiple consumer instances in the same consumer group, each in its own thread. Kafka assigns partitions to the consumers in the group, and a partition is consumed by exactly one consumer, which enables parallel work across the group. Therefore, per thread there is one consumer, and that consumer should not be multi-threaded. You can still process messages concurrently by handing off records to a worker pool after polling, but the consumer object itself remains single-threaded.

A Kafka consumer is not thread-safe, so one thread should own a single consumer instance and use it in that thread only. If you need parallelism, run multiple consumer instances in the same consumer group, each in its own thread. Kafka assigns partitions to the consumers in the group, and a partition is consumed by exactly one consumer, which enables parallel work across the group. Therefore, per thread there is one consumer, and that consumer should not be multi-threaded. You can still process messages concurrently by handing off records to a worker pool after polling, but the consumer object itself remains single-threaded.