When building event-driven applications, you may want to publish events to downstream consumers. Amazon EventBridge allows you to configure rules and targets to create consumers of events.

Amazon EventBridge allows you to listen to events raised in various AWS Services, and also create and publish your own custom events. Once an event is published to your event bus, EventBridge will process these events and trigger your downstream consumers (targets).

What are Targets?

• When you publish an event, you want a downstream consumer to react. Targets are consumers of your events.

• A target cannot live without an EventBridge rule. Rules process events before they reach downstream targets.

• When an event triggers a rule all of the targets associated with the rule are invoked (unless you have filtering setup on your rule)

• Targets are services, resources or end points you want your event to trigger (read the full list here).

• Targets can also be services in other AWS accounts or Regions. This allows you to setup multi bus topologies within your architecture. Read more.

Target Permissions

• Your EventBridge bus will need permissions to trigger downstream targets.

• To make API calls against the resources you own, EventBridge needs the appropriate permissions. For Lambda, Amazon SNS, Amazon SQS, and Amazon CloudWatch Logs resources, EventBridge uses resource-based policies. For Kinesis streams, EventBridge uses identity-based policies. You can read more here.

Fan out to many services

• EventBridge is a fully managed serverless service that allows you to fan out events to downstream consumers. (also known as publish/subscribe pattern)

• Using events you can notify downstream consumers that something has happened. These producers of events can be AWS service events or even custom events.

• Custom events are powerful. They allow you to notify downstream consumers that something has happened. These can be important business domain events, or maybe technical events. When developing your events it's important to understand event design and the different types of events you may raise.

Targets with additional properties

• EventBridge supports 28+ different targets, these can be AWS Services and also external APIS using API Destinations.

• Depending on what target you configure, you may have the option to add additional configuration to your targets.

Extra Resources

• EDA Visuals - Explore over 40 visuals about event-driven architectures, learn the fundamentals and advanced concepts. Dive deeper and explore resources linked to every resource.

• Publishing events without targets - When publishing events, you may not know of downstream consumers, or even have any, but one great practice of EDA is you may want to publish events without any consumers (yet). This visual helps you understand more.

• Using EventBridge with legacy applications - Event driven applications are not just for green field projects, but using events can help you migrate off legacy systems. Maybe Amazon EventBridge can help you here with your migration into the cloud?

• Flow Architectures - Great book by James Urquhart about how events can and will be used to communicate between organisations, when using EventBridge you may want to explore API Destinations being able to trigger internal/external APIS with your events, creating and moving to a flow architecture.

• What are producer and consumer responsibilities? - When building your EDA application your producers and consumers will have their own set of responsibilities, this visual can help you understand more.

• Understanding event types - When you publish events, there are many types of events to consider, this visual helps you understand them and dive deeper.

• Awesome EventBridge - A list of resources from blogs, videos and examples all about EventBridge. Feel free to explore or even contribute to the list.