Glossary

Consumer group (Kafka)

A Kafka consumer group is a set of consumer instances that cooperatively consume a topic. Kafka assigns each partition to exactly one consumer in the group at any time, ensuring each message is processed by exactly one consumer and that messages within a partition are processed in order. Adding consumers increases parallelism up to the partition count; beyond that, additional consumers are idle.

Formula: Parallel consumers per group ≤ partition count per subscribed topic.

Last updated: March 2026