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

The characteristic that makes a message idempotent in Kafka is that it can be sent multiple times without adverse effects. This means that if a message is produced more than once due to a failure in delivery or acknowledgment, the outcome remains the same as if it had been sent only once. Idempotency is crucial in systems like Kafka to ensure that processing the same message multiple times does not lead to duplicate data or unintended side effects, which is particularly important for ensuring data integrity in distributed systems.

The other options do not accurately pertain to idempotency. A message being large and complex does not inherently grant it idempotent properties; it could still result in different outcomes if sent multiple times. Immediate acknowledgment is related to message delivery guarantees but does not ensure that multiple sends of the same message are harmless; it simply addresses delivery confirmation. Lastly, while a unique identifier can help track messages and their states, it does not alone make a message idempotent; rather, it is the ability to safely reprocess a message without changing the outcome that defines idempotency.