Purpose of pubsub frameworks?

Question

Highload

Hello, I don’t quite understand for what tasks such things are used, to build distributed systems?
For example https://github.com/bitly/nsq . That is, I can accept requests and distribute tasks to nodes in the cluster? Balancing?
Give an example of a situation where such things apply
Thank you

Answer 1

For delayed execution of long tasks, scaling, balancing, limiting simultaneously running processes (so that workers gradually take tasks from the queue, and not take them en masse, while requiring more resources than they have).
Example: any long-term tasks (video processing for example).
You can also use pub/sub for all kinds of chats, for example. And in general, where messaging is needed.