Messaging

Use of asychronous processing
instead of telling the system what to do step by step, we break down the work into smaller pieces and let it decide the optimal execution order.
- As a result, things become much more dynamic, but also more unpredictable
Helps to scale applications and increase fault tolerance

Uses

Decouple producers and consumers, asynchronous processing
- consumer does not need to be up for message to be processed
Improve reliable communication
- req resp via two message queues
Can increase scalability
- Add more replica consumers to a queue
Buffer in front of services
- Prevent overloading a service
- reduce timeouts
A means of retry an event
- if an event fails, it can send the message back to the same queue it retrieved the message and reprocess again later
- Based on a cron job, can consumer a messsage at a specificed time
Can parallelise requests
- pub sub same messages can be handled by multiple (same or different consumers)
- queue - multiple different messages can be handled by different consumers
Can place errored messages on a dead letter queue which can handled separately
For long running processes, background jobs, batch jobs
when you dont need to cater for immediate responses or need to be part of a basic transaction

https://stackify.com/message-queues-12-reasons/
https://www.quora.com/What-are-some-use-cases-for-message-queues-in-real-life-and-what-are-some-architectures-that-achieve-the-same-goal-without-using-queues-explicitly
https://blog.iron.io/top-10-uses-for-message-queue/

https://www.programmableweb.com/news/why-messaging-queues-suck/analysis/2017/02/13
https://techblog.bozho.net/you-probably-dont-need-a-message-queue/
https://www.reddit.com/r/programming/comments/arjaee/counter_arguments_to_using_message_queuesbrokers/