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

Allowing an out-of-sync replica to become a leader can pose significant risks to message integrity within the Kafka system. When a replica that has not fully replicated all messages from the leader takes on the leadership role, it can lead to scenarios where messages that were committed to the previous leader but not yet replicated to the new leader may be lost or become inaccessible. This happens because the new leader lacks the complete data set that should have been maintained across the replicas, thus risking data consistency and integrity.

While other options present benefits like message guarantees or availability improvements, they are not applicable in this scenario. The core risk associated with promoting an out-of-sync replica lies in the potential for data loss, thereby highlighting the critical nature of maintaining synchronized replicas before a server shift occurs. This underscores the importance of having replicas in sync for maintaining the overall robustness and reliability of Kafka's data streaming capabilities.