How will the system behavior change if another consumer is added with a fixed number of partitions?

If you have a fixed number of partitions in the system, for example in Kafka, and you add another consumer to the group, the behavior will change as follows:

• Partitions are distributed among all consumers in the group.
• When the number of consumers exceeds the number of partitions, some consumers will have no assigned partitions and thus no load.
• If the number of consumers is less than or equal to the number of partitions, each consumer gets one or more partitions.

Therefore, adding a consumer with a fixed number of partitions can lead to a decrease in load per consumer, but if more consumers are added than partitions, some will be idle.