How many unique consumers were there per partition?

In Kafka, there can be only one active consumer per partition within a consumer group. This is because Kafka guarantees message order within a partition, and to avoid conflicts, a partition is assigned to only one consumer in the group.

If there are more consumers than partitions in the group, some consumers will be idle, as partitions cannot be shared among multiple consumers simultaneously.

Therefore, the number of unique consumers per partition is exactly one.