At-most-once delivery in Kafka - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does At-most-once delivery mean in message systems like Kafka?

It means each message is delivered zero or one time. Messages might be lost but never duplicated.

intermediate

How does Kafka achieve at-most-once delivery?

By committing the message offset before processing, so if a failure happens, some messages might be skipped but never repeated.

beginner

What is a risk of at-most-once delivery?

Messages can be lost if a failure happens after committing the offset but before processing the message.

intermediate

Compare at-most-once and at-least-once delivery.

At-most-once: messages delivered zero or one time (no duplicates, possible loss).<br>At-least-once: messages delivered one or more times (no loss, possible duplicates).

beginner

Why might a system choose at-most-once delivery?

To prioritize speed and simplicity over guaranteed delivery, especially when losing some messages is acceptable.

In Kafka, what happens if you commit the offset before processing a message?

A Messages are duplicated.

B You get at-least-once delivery.

C You get exactly-once delivery.

D You get at-most-once delivery.

Committing offset before processing means messages might be skipped if failure occurs, so at-most-once delivery is achieved.

Which delivery guarantee allows message loss but no duplicates?

A At-most-once

B Exactly-once

C At-least-once

D None

At-most-once delivery can lose messages but never delivers duplicates.

What is a downside of at-most-once delivery?

A Messages may be duplicated.

B Messages may be lost.

C Processing is slower.

D It requires complex coordination.

At-most-once delivery risks losing messages if failures happen after offset commit.

If you want to avoid duplicates but can accept some message loss, which delivery mode fits best?

A At-most-once

B At-least-once

C Exactly-once

D No delivery

At-most-once delivery avoids duplicates but may lose messages.

Which Kafka feature controls which messages a consumer has processed?

A Topic partition

B Producer ID

C Offset

D Broker

Offset tracks the position of the consumer in the message stream.

Explain in your own words what at-most-once delivery means and how Kafka can implement it.

Think about when the offset is saved and what happens if a failure occurs.

Describe the trade-offs between at-most-once and at-least-once delivery in Kafka.

Consider what happens if a failure occurs before or after processing.