An event bus in AWS, specifically in Amazon EventBridge, is the routing layer that receives events and sends them to one or more targets based on rules. Think of it as a smart message hub: producers send events in, rules inspect them, and the right AWS services or apps get the events they need.

What it does

  • Receives events from AWS services, custom apps, or SaaS partners.
  • Uses rules to match events and optionally transform them before delivery.
  • Routes events to targets such as Lambda, SQS, SNS, Step Functions, and others.

Main bus types

  • Default event bus: created automatically in every AWS account and receives events from AWS services.
  • Custom event bus: used for your own applications and workflows.
  • Partner event bus: used for events from supported SaaS partners.

Simple example

If an S3 upload happens, EventBridge can put that event on the bus, a rule can match it, and then a Lambda function can run to process the file.

In one line

An AWS event bus is the central router for event-driven systems on EventBridge, helping decouple services so they can react to changes without tight coupling.