Amazon EventBridge

Serverless event bus — routes events from AWS services, SaaS partners, and custom applications to targets using content-based filtering rules.

Overview

Amazon EventBridge is a serverless event bus that connects applications using events — it ingests events from AWS services, SaaS integrations, and custom sources, then routes them to targets based on rules with fine-grained content filtering.

EventBridge replaces the older CloudWatch Events service and extends it with schema discovery, third-party SaaS integration, and cross-account/cross-region event delivery.

Core Concepts

Concept	Description
Event Bus	A channel that receives events; each account has a default bus plus custom buses
Event	A JSON object describing a state change (source, detail-type, detail, time, etc.)
Rule	Matches incoming events on a bus and routes them to one or more targets
Event Pattern	JSON pattern on a rule that filters events by source, detail-type, or detail fields
Schedule	A cron or rate expression that triggers a rule on a time-based schedule
Target	The destination that receives matched events (Lambda, SQS, Step Functions, etc.)
Schema Registry	Auto-discovered or manually registered event schemas for code generation
Pipe	Point-to-point integration: source → optional filter → optional enrichment → target
Archive	Stores events for replay; configurable retention period
Replay	Re-sends archived events to the event bus for reprocessing

How EventBridge Works

Event Sources                   Event Bus              Rules + Targets
┌──────────────┐
│ AWS Services │─────┐
│ (S3, EC2...) │     │
└──────────────┘     │     ┌─────────────┐     ┌──────────────────────┐
                     ├────▶│  Event Bus  │────▶│ Rule: pattern match  │
┌──────────────┐     │     │  (default   │     │   → Target: Lambda   │
│ SaaS Partners│─────┤     │   or custom)│     │   → Target: SQS      │
│ (Zendesk,    │     │     └─────────────┘     │   → Target: Step Fn  │
│  Datadog...) │     │           │              └──────────────────────┘
└──────────────┘     │           ▼
                     │     ┌─────────────┐
┌──────────────┐     │     │   Archive   │────▶ Replay
│ Custom Apps  │─────┘     └─────────────┘
│ (PutEvents)  │
└──────────────┘

Event Pattern Examples

Match EC2 instance state changes to "stopped":

{
  "source": ["aws.ec2"],
  "detail-type": ["EC2 Instance State-change Notification"],
  "detail": {
    "state": ["stopped"]
  }
}

Content-based filtering with prefix and numeric matching:

{
  "source": ["custom.orders"],
  "detail": {
    "amount": [{ "numeric": [">", 1000] }],
    "region": [{ "prefix": "us-" }]
  }
}

Supported Targets

Target Category	Examples
Compute	Lambda, ECS task, Batch job, EC2 (via SSM Run Command)
Messaging	SQS, SNS, Kinesis Data Stream, Kinesis Data Firehose
Orchestration	Step Functions state machine, CodePipeline
API	API Gateway, API Destination (third-party HTTP endpoints)
Cross-account/region	Event bus in another account or region
Logging	CloudWatch Log Group

EventBridge Pipes

Source (SQS, Kinesis, DynamoDB Stream, Kafka)
    → Filter (event pattern)
        → Enrichment (Lambda, Step Functions, API Gateway, API Destination)
            → Target (any supported target)

Pipes provide a simpler point-to-point model without needing an event bus — useful for stream-to-target integrations with optional transformation.

Criteria	EventBridge	SNS	SQS
Model	Event bus + content-based routing	Pub/sub fan-out	Queue (point-to-point)
Filtering	Rich JSON content filtering	Attribute-based filter policies	No native filtering
SaaS integration	Yes — built-in partner sources	No	No
Schema discovery	Yes	No	No
Archive and replay	Yes	No	No (DLQ for failed messages)
Throughput	Varies by region (soft limit)	Nearly unlimited	Nearly unlimited
Latency	Sub-second (slightly higher)	Sub-second	Sub-second

Common Use Cases

Event-driven microservices — Decouple producers and consumers using content-based routing rules on a shared event bus.
SaaS integration — Ingest events from Zendesk, Auth0, Datadog, or Stripe directly into AWS workflows.
Scheduled automation — Use cron/rate rules to trigger Lambda functions on a schedule (replaces CloudWatch Events schedules).
Cross-account event routing — Forward events from application accounts to a central security or analytics account.
Audit trail replay — Archive all events and replay a specific time window to reprocess or debug.

SAA/SAP Exam Tips

SAA Tip: "Route events based on content" or "filter events by detail fields" → EventBridge. SNS filter policies are simpler; EventBridge offers richer JSON-based matching.

SAA Tip: "Receive events from SaaS partners" → EventBridge partner event source. No other AWS messaging service has native SaaS integrations.

SAP Tip: EventBridge has a default throughput limit per region (can be raised). For very high-throughput streaming (millions of events/s), Kinesis Data Streams is more appropriate.

Cross-Cloud Equivalents

Provider	Service / Solution	Notes
AWS	Amazon EventBridge	Baseline
Azure	Azure Event Grid	Event routing with filtering; similar model
GCP	Eventarc	Event routing for Cloud Run and Cloud Functions
On-Premises	Apache Kafka, RabbitMQ (with plugins), NATS	Requires custom routing logic

Pricing Model

Dimension	Unit	Notes
Custom events	Per million events	Published via PutEvents API
AWS/partner events	Free	AWS service events and partner events at no cost
Schema discovery	Free	Included at no additional charge
Archive + replay	Per GB archived	Replay events incur per-event charges
Pipes	Per million requests	Plus data processing per GB

Amazon SQS and SNS — queue and pub/sub messaging for simpler patterns
AWS Step Functions — orchestrate multi-step workflows triggered by EventBridge
Amazon CloudWatch — EventBridge replaces CloudWatch Events (same underlying service)
AWS Lambda — most common EventBridge target for serverless processing

Amazon EventBridge

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