Apache Kafka Complete Practice Exam 2025 – All-in-One Prep

Kafka ensures message durability primarily through writing messages to disk and replicating them across brokers. When a message is produced in Kafka, it is first stored in a log file on disk. This means that even if a broker crashes or is otherwise unavailable, the messages are not lost; they can be retrieved when the broker comes back online.

Replication adds an additional layer of durability. Kafka allows you to configure the number of replicas for each partition of a topic. When a message is produced, it is not only written to the disk of the leader broker for that partition but is also replicated to one or more follower brokers. This means that if the leader fails, one of the followers can take over without causing any message loss, ensuring high availability and durability of messages.

This mechanism contrasts sharply with other options. Storing messages only in memory would lead to data loss if a broker fails. Regularly backing up data to a separate server is not a typical part of Kafka's operational model, as it is designed for real-time processing and high throughput. Similarly, while compressing messages does help in saving space, it does not contribute to the durability of messages themselves. Thus, writing to disk and replicating across brokers is the core strategy Kafka employs to ensure