Thanks Rahul,

Let’s imagine there are four partitions and five consumers from the same consumer group. Obviously, the fifth consumer is sitting idle.

What if one of the active consumers goes down? In that case, the idling consumer can quickly join and resume from where the fallen consumer left off. The transition would be immediate. Hence, the name hot failover.

If we had only four consumers, then Kafka will trigger a partition rebalance and assign one of the remaining consumers the partitions consumed by crashed consumer. That could take some time.

That is my understanding. But other opinions are welcome as well.