What will happen if there are two partitions and three consumers in one group? And if there are three partitions and two consumers?

In Kafka, the number of partitions determines the maximum number of consumers that can read from a topic simultaneously within a single group.

• If there are fewer partitions than consumers (2 partitions and 3 consumers), then one consumer will be left without assigned partitions and will not receive messages.
• If there are more partitions than consumers (3 partitions and 2 consumers), then some consumers will read from multiple partitions. For example, one consumer may read from 2 partitions, and another from 1.

Thus, Kafka guarantees that each partition is assigned to exactly one consumer in the group, but a consumer can process multiple partitions.