Grokking the System Design Interview, Volume II
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Kafka Delivery Semantics

Let's explore what message delivery guarantees Kafka provides to its clients.

Producer delivery semantics

As we know, a producer writes only to the leader broker, and the followers asynchronously replicate the data. How can a producer know that the data is successfully stored at the leader or that the followers are keeping up with the leader? Kafka offers three options to denote the number of brokers that must receive the record before the producer considers the write as successful:

  • Async: Producer sends a message to Kafka and does not wait for acknowledgment from the server

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Amey Naik

· 5 years ago

Kafka Delivery Semantics: [At-least-once] "Thus, duplicate message delivery could happen in such a scenario."

how is the duplicate message delivery happening? If the consumer crashes, I just need to just send the same message to the consumer again. Correct?

Can you please throw some light on how this is different from "Exactly-once"?

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Gokul S

· 4 years ago

Under the Consumer Delivery Semantics of Kafka, the At-least-once and Exactly once seem to do the same thing.

  1. At-least-once scenario is that a consumer reads and waits until processing is over before committing. 2,Exactly-once says that the consumer puts the message processing and the offset increment in one transaction. What is the difference?