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

The safest acknowledgment scheme in Kafka is achieved using the configuration where acks is set to 'all'. When you use this acknowledgment setting, it ensures that the leader broker sends the message to all in-sync replicas (ISRs) before acknowledging the message to the producer. This means that the message must be fully replicated across all replicas that are currently in sync, which significantly reduces the risk of data loss in the event of a broker failure.

If the producer receives an acknowledgment, it can be confident that all ISRs have received the message, ensuring durability and high availability. This level of acknowledgment is particularly important in scenarios where data integrity is critical, such as in financial transactions or systems where losing even a single message could have serious consequences.

In contrast, the other acknowledgment settings provide different guarantees:

- Setting acks to zero means that the producer does not wait for any acknowledgment from the brokers, effectively making the process the fastest but leaving ample room for data loss.

- Acks set to one ensures that the leader broker acknowledges the message after it is written, but if the leader fails before the data has been replicated to the followers, it could also lead to data loss.

- Configuring acknowledgments manually is not a predefined scheme and does not inherently