Apache Kafka order of messages with multiple partitions

Question

As per Apache Kafka documentation, the order of the messages can be achieved within the partition or one partition in a topic. In this case, what is the parallelism benefit

Answer 1

Traditional MQ works in a way such that once a message has been processed, it gets removed from the queue. A message queue allows a bunch of subscribers to pull a message, or a batch of messages, from the end of the queue. Queues usually allow for some level of transaction when pulling a message off, to ensure that the desired action was executed, before the message gets removed, but once a message has been processed, it gets removed from the queue.

With Kafka on the other hand, you publish messages/events to topics, and they get persisted. They don’t get removed when consumers receive them. This allows you to replay messages, but more importantly, it allows a multitude of consumers to process logic based on the same messages/events.

You can still scale out to get parallel processing in the same domain, but more importantly, you can add different types of consumers that execute different logic based on the same event. In other words, with Kafka, you can adopt a reactive pub/sub architecture. ref: https://hackernoon.com/a-super-quick-comparison-between-kafka-and-message-queues-e69742d855a8