Apache Kafka Practice Exam 2026 – The Complete All-in-One Guide for Exam Success!

When a producer sets the acknowledgment configuration to "acks = all," it requires the leader broker to wait for acknowledgment not just from the leader itself but also from all in-sync replicas. This configuration ensures that messages are considered successfully written only when they are fully replicated to all in-sync replicas, providing a higher level of durability and reliability.

This behavior is crucial in scenarios where data loss is not acceptable, as it guarantees that the message is safely stored across multiple brokers. If the leader receives acknowledgments from all in-sync replicas, only then will it confirm the write to the producer. This approach contrasts with other acknowledgment settings; for example, when ack is set to "1," the message is considered successfully sent as soon as the leader broker persists it, irrespective of the state of the replicas.

Overall, using "acks = all" enhances data integrity and durability in a Kafka system, making it suitable for critical data streams where ensuring that messages are fully replicated is essential.