What is the role of a consumer group in a message processing or queue system?

A consumer group in message processing systems or queues plays a key role in scaling and load balancing.

Main functions of a consumer group:

• Message distribution: Messages from a queue or topic are distributed among all consumers in the group so that each processes its part of the data.
• Parallel processing: Allows messages to be processed in parallel, increasing the system's throughput.
• Delivery guarantee: Each specific consumer in the group receives a unique set of messages, preventing duplicate processing.
• Fault tolerance: If one consumer fails, others in the group can take over its tasks.

For example, in Apache Kafka, a consumer group allows multiple applications to read from a single topic in parallel, with each message being processed by only one consumer in the group.