Conquer Apache Kafka 2025 – Dive into Data Streaming Dominance!

During an Unclean Leader Election, an out-of-sync replica can indeed become the leader. This situation arises when the original leader broker is unable to participate in the election process, often due to failure or being out of the cluster. In this case, Kafka prioritizes availability over consistency, allowing a replica that may not have the latest data to take over as the leader. This can result in data inconsistency because the new leader might not have all the updates that the original leader had.

This behavior is designed to minimize downtime in situations where maintaining high availability is crucial, even if it means risking some data inconsistency. Unclean leader elections often occur in environments configured with the default settings where a broker can lead without needing to be fully caught up.

The other options do not accurately reflect the concept of Unclean Leader Election. For instance, replicas are not immediately reset, nor is there a guarantee that the original leader will be restored automatically. Additionally, one of the defining characteristics of an Unclean Leader Election is that it does not guarantee data consistency, which contradicts the idea that data is always guaranteed to be consistent.