System Design: The Pub-sub Abstraction

What is a pub-sub system?

Publish-subscribe messaging, often known as pub-sub messaging, is an asynchronous service-to-service communication method that’s popular in serverless and microservices architectures. Messages can be sent asynchronously to different subsystems of a system using the pub-sub system. All the services subscribed to the pub-sub model receive the message that’s pushed into the system.

For example, when a famous athlete posts on Instagram or shares a tweet, all of their followers are updated. Here, the athlete is the publisher, their post or tweet is the message, and all of their followers are subscribers.