Amazon EventBridge
A serverless event bus that routes events from AWS services, SaaS applications, and custom applications, serving as the backbone of event-driven architectures
Overview
Amazon EventBridge (formerly CloudWatch Events) is a serverless event bus that loosely couples event sources with event targets. It filters events from AWS services (EC2 instance state changes, S3 object creation, CodePipeline deployment results, etc.), SaaS partners (Zendesk, Datadog, Auth0, etc.), and custom applications based on rules, routing them to over 20 targets including Lambda, SQS, SNS, Step Functions, and API Gateway. Event pattern matching allows you to process only events that match specific conditions.
Event Bus and Rule Design
An EventBridge event bus is a channel through which events flow. The default event bus receives AWS service events, custom event buses receive application-specific events, and partner event buses receive SaaS partner events. The AWS user guide calls this rules-and-targets type of custom bus Custom Event Bus - Classic; it keeps the Classic type available and advises starting new applications with the Custom Event Bus, to which consumers attach their own subscribers (as of October 2026). Rules route events to targets based on event patterns (JSON filter conditions) or schedules (cron or rate expressions). Event patterns can filter on event source, type, and detail field values. Available filtering operators include prefix match, suffix match, numeric range, and existence checks. Each rule can have up to 5 targets, enabling fan-out patterns that deliver a single event to multiple targets simultaneously.
Scheduler and Pipes
EventBridge Scheduler invokes targets on a schedule defined by cron or rate expressions. The AWS user guide describes EventBridge scheduled rules as a legacy feature and recommends Scheduler for invoking targets on a schedule (as of October 2026). Features include one-time schedules (execute once at a specific date and time), timezone specification, and flexible time windows (execute within a specified time range). EventBridge Pipes simplifies point-to-point integration from source to target. It retrieves events from sources such as SQS queues, Kinesis streams, and DynamoDB streams, applies optional filtering and enrichment (for example, transformation via Lambda), and delivers them to targets. With Pipes, integrations such as SQS to Step Functions need less code in between.
Usage Patterns in Practice
A representative use of EventBridge is automation based on AWS service events: notifying Slack when an EC2 instance enters the terminated state, automatically modifying security groups when GuardDuty detects a threat, or alerting the team when a CodePipeline deployment fails. In microservices architectures, one approach is an event-driven pattern that uses the event bus for inter-service communication. For example, an order service publishes an "order confirmed" event to EventBridge, and the inventory service, payment service, and notification service each independently process the event. The Azure equivalent is Azure Event Grid, which similarly enables event-driven architectures.
References (Official AWS Resources)
The primary sources for this page are the official AWS website and documentation. Check the official pages below for the latest specifications and pricing.
- AWS Lambda official page
- Amazon SQS official page
- AWS Step Functions official page
- AWS Documentation (official)
If this page and the official documentation disagree, treat the official documentation as authoritative.