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

When the configuration for acknowledgments (acks) is set to 1 in Apache Kafka, it indicates that the leader broker will acknowledge the receipt of the message once it has been successfully written to its local partition. This means that as soon as the leader acknowledges that the write operation to its own log is complete, it will inform the producer that the message has been successfully sent.

This setting provides a balance between performance and data reliability. Since the acknowledgment occurs after the data is safely stored in the leader's partition, it means the producer can proceed with its next operation without waiting for acknowledgments from replicas. However, it does not guarantee that the data has been replicated to all followers, which can lead to data loss if the leader fails immediately after sending the acknowledgment but before the replicas have a chance to replicate the message.

In essence, setting acks to 1 ensures that the producer receives confirmation promptly after the data is written to the leader's partition while not requiring confirmation from all replicas, which is characteristic of the other options.