AWS EventBridge Rule Builder

About This Tool

Amazon EventBridge is a serverless event bus that routes events from AWS services, SaaS applications, and custom sources to targets like Lambda, SQS, Step Functions, and API destinations. Rules define which events match and where to send them using event patterns — JSON structures that filter on event source, detail-type, account, region, and custom detail fields. Writing event patterns requires understanding exact-match, prefix, numeric range, exists, and anything-but matchers. The EventBridge Rule Builder helps you construct rules with correct event pattern syntax, target configurations, input transformations, and dead-letter queue settings.

When to Use This Tool

• •Building a rule that captures EC2 instance state changes (running, stopped, terminated) and routes them to a Lambda function for inventory tracking
• •Creating content-based filtering rules that match S3 object creation events only for specific prefixes and file extensions
• •Designing cross-account event routing rules that send security-relevant CloudTrail events to a central security account event bus
• •Generating rules with input transformers that extract specific fields from events and format them for downstream targets like SNS notifications

Frequently Asked Questions

How do EventBridge event patterns work?

Event patterns are JSON objects that match against incoming events using structural comparison. Each field in the pattern is matched against the corresponding field in the event. Values can be exact strings, arrays (OR logic), numeric ranges, prefix matches, suffix matches, or anything-but exclusions. Only fields present in the pattern are evaluated — omitted fields match any value. All specified fields must match for the rule to trigger (AND logic between fields).

What is the difference between EventBridge and SNS for event routing?

EventBridge supports content-based filtering on event payload fields, while SNS message filtering is limited to message attributes. EventBridge has a richer set of pattern matchers (prefix, numeric range, exists, anything-but), native integrations with SaaS event sources, schema discovery, and event replay. SNS is simpler and better for high-throughput fan-out to many subscribers where content filtering is not required. EventBridge also supports archive and replay for debugging.

How do input transformers work in EventBridge rules?

Input transformers let you reshape the event before delivering it to the target. They have two components: an input paths map that extracts values from the event using JSONPath expressions, and an input template that defines the output structure using those extracted values as variables. This avoids writing Lambda functions just to reformat event data. For example, you can extract instance-id and state from an EC2 event and format a human-readable message for SNS.

Related Learning Guides

• SQS vs SNS vs EventBridge25 min read