What is AWS EventBridge?

Amazon EventBridge (formerly CloudWatch Events) is a serverless event bus service that connects application components using events. It enables event-driven architectures across AWS services, SaaS applications, and custom applications. Core concepts: Event: JSON document indicating something happened (EC2 instance state change, S3 object created, CodePipeline stage changed, custom application event); Event Bus: Default bus (AWS service events), Custom bus (your application events), Partner bus (SaaS integration — Datadog, Zendesk, PagerDuty); Rule: matches events based on event pattern or schedule → routes to targets; Targets: where events are sent — Lambda, SQS, SNS, ECS task, Step Functions, Kinesis, API Gateway, CodeBuild, EC2 Auto Scaling, EventBridge bus (cross-account/region). Event patterns: match on any JSON field: {"source": ["aws.ec2"], "detail-type": ["EC2 Instance State-change Notification"], "detail": {"state": ["terminated"]}} → trigger cleanup Lambda. Scheduled rules: cron expression or rate expression: rate(1 hour), cron(0 8 * * ? *) — trigger Lambda daily at 8 AM UTC. Event Archive and Replay: archive events for debugging/compliance; replay to reprocess historical events. Schema Registry: discover and store event schemas — generate code bindings. Pipes: point-to-point integration between a source (SQS, DynamoDB Streams, Kinesis) and target with optional filtering and enrichment. vs SNS: EventBridge supports content-based filtering, schema registry, archive/replay, third-party SaaS. SNS is simpler for basic fan-out.