Apache Kafka Practice Exam 2025 – The Complete All-in-One Guide for Exam Success!

When the configuration parameter min.insync.replicas is set to 2 for a topic that has 3 replicas, it establishes a requirement that at least two of those replicas must be in sync with the leader replica for a write operation to be successful. This setting is crucial for ensuring data durability and availability in a distributed system like Apache Kafka.

This configuration helps maintain a balance between availability and fault tolerance. If a write request is received, Kafka will check how many replicas are currently in sync with the leader. If at least two replicas are in sync, the write will proceed. This requirement prevents data loss in scenarios where one of the replicas may fail or become in sync for any reason, ensuring that there remains a certain number of replicas that can provide a valid copy of the data.

If fewer than two replicas are in sync, Kafka rejects the write request to avoid scenarios where data could be lost in the event of a failure in one or more replicas. Therefore, setting min.insync.replicas to 2 enhances the resilience of the system by ensuring that sufficient replicas are available for consistency during writes.