Channel that receives events. Types:

Default: Receives AWS service events
Custom: Your application events
Partner: SaaS application events

Rules

Match incoming events and route to targets. Each rule can have up to 5 targets.

Event Patterns

JSON patterns that define which events match a rule.

Targets

AWS services that receive matched events (Lambda, SQS, SNS, Step Functions, etc.).

Scheduler

Schedule one-time or recurring events to invoke targets.

Common Patterns

Create Custom Event Bus and Rule

AWS CLI:

# Create custom event bus
aws events create-event-bus --name my-app-events

# Create rule
aws events put-rule \
  --name order-created-rule \
  --event-bus-name my-app-events \
  --event-pattern '{
    "source": ["my-app.orders"],
    "detail-type": ["Order Created"]
  }'

# Add Lambda target
aws events put-targets \
  --rule order-created-rule \
  --event-bus-name my-app-events \
  --targets '[{
    "Id": "process-order",
    "Arn": "arn:aws:lambda:us-east-1:123456789012:function:ProcessOrder"
  }]'

# Add Lambda permission
aws lambda add-permission \
  --function-name ProcessOrder \
  --statement-id eventbridge-order-created \
  --action lambda:InvokeFunction \
  --principal events.amazonaws.com \
  --source-arn arn:aws:events:us-east-1:123456789012:rule/my-app-events/order-created-rule

boto3:

import boto3

events = boto3.client('events')

# Create event bus
events.create_event_bus(Name='my-app-events')

# Create rule
events.put_rule(
    Name='order-created-rule',
    EventBusName='my-app-events',
    EventPattern=json.dumps({
        'source': ['my-app.orders'],
        'detail-type': ['Order Created']
    }),
    State='ENABLED'
)

# Add target
events.put_targets(
    Rule='order-created-rule',
    EventBusName='my-app-events',
    Targets=[{
        'Id': 'process-order',
        'Arn': 'arn:aws:lambda:us-east-1:123456789012:function:ProcessOrder'
    }]
)

Publish Custom Events

import boto3
import json

events = boto3.client('events')

events.put_events(
    Entries=[
        {
            'Source': 'my-app.orders',
            'DetailType': 'Order Created',
            'Detail': json.dumps({
                'order_id': '12345',
                'customer_id': 'cust-789',
                'total': 99.99,
                'items': [
                    {'product_id': 'prod-1', 'quantity': 2}
                ]
            }),
            'EventBusName': 'my-app-events'
        }
    ]
)

Scheduled Events

# Run every 5 minutes
aws events put-rule \
  --name every-5-minutes \
  --schedule-expression "rate(5 minutes)"

# Run at specific times (cron)
aws events put-rule \
  --name daily-cleanup \
  --schedule-expression "cron(0 2 * * ? *)"

# Add target
aws events put-targets \
  --rule every-5-minutes \
  --targets '[{
    "Id": "cleanup-function",
    "Arn": "arn:aws:lambda:us-east-1:123456789012:function:Cleanup"
  }]'

EventBridge Scheduler (One-Time and Flexible)

# One-time schedule
aws scheduler create-schedule \
  --name send-reminder \
  --schedule-expression "at(2024-12-25T09:00:00)" \
  --target '{
    "Arn": "arn:aws:lambda:us-east-1:123456789012:function:SendReminder",
    "RoleArn": "arn:aws:iam::123456789012:role/scheduler-role",
    "Input": "{\"message\": \"Merry Christmas!\"}"
  }' \
  --flexible-time-window '{"Mode": "OFF"}'

# Recurring with flexible window
aws scheduler create-schedule \
  --name hourly-sync \
  --schedule-expression "rate(1 hour)" \
  --target '{
    "Arn": "arn:aws:lambda:us-east-1:123456789012:function:SyncData",
    "RoleArn": "arn:aws:iam::123456789012:role/scheduler-role"
  }' \
  --flexible-time-window '{"Mode": "FLEXIBLE", "MaximumWindowInMinutes": 15}'

AWS Service Events

# EC2 state changes
aws events put-rule \
  --name ec2-state-change \
  --event-pattern '{
    "source": ["aws.ec2"],
    "detail-type": ["EC2 Instance State-change Notification"],
    "detail": {
      "state": ["stopped", "terminated"]
    }
  }'

# S3 object created
aws events put-rule \
  --name s3-upload \
  --event-pattern '{
    "source": ["aws.s3"],
    "detail-type": ["Object Created"],
    "detail": {
      "bucket": {"name": ["my-bucket"]},
      "object": {"key": [{"prefix": "uploads/"}]}
    }
  }'

CLI Reference

Event Buses

Command	Description
`aws events create-event-bus`	Create event bus
`aws events delete-event-bus`	Delete event bus
`aws events list-event-buses`	List event buses
`aws events describe-event-bus`	Get event bus details

Rules

Command	Description
`aws events put-rule`	Create or update rule
`aws events delete-rule`	Delete rule
`aws events list-rules`	List rules
`aws events describe-rule`	Get rule details
`aws events enable-rule`	Enable rule
`aws events disable-rule`	Disable rule

Targets

Command	Description
`aws events put-targets`	Add targets to rule
`aws events remove-targets`	Remove targets
`aws events list-targets-by-rule`	List rule targets

Events

Command	Description
`aws events put-events`	Publish events

Best Practices

Event Design

Use meaningful source names — company.service.component
Use descriptive detail-types — Order Created, User Signed Up
Include correlation IDs for tracing
Keep events small (< 256 KB)
Use versioning for event schemas

# Good event structure
{
    'Source': 'mycompany.orders.api',
    'DetailType': 'Order Created',
    'Detail': json.dumps({
        'version': '1.0',
        'correlation_id': 'req-abc-123',
        'timestamp': '2024-01-15T10:30:00Z',
        'order_id': '12345',
        'data': {...}
    })
}

Reliability

Use DLQs for failed deliveries
Implement idempotency in consumers
Monitor failed invocations
Use archive and replay for recovery

Security

Use resource policies to control access
Enable encryption with KMS
Use IAM roles for targets

Cost Optimization

Use specific event patterns to reduce matches
Batch events when publishing (up to 10 per call)
Archive selectively — not all events

Troubleshooting

Rule Not Triggering

Debug:

# Check rule status
aws events describe-rule --name my-rule

# Check targets
aws events list-targets-by-rule --rule my-rule

# Test event pattern
aws events test-event-pattern \
  --event-pattern '{"source": ["my-app"]}' \
  --event '{"source": "my-app", "detail-type": "Test"}'

Common causes:

Rule disabled
Event pattern doesn't match
Target permissions missing

Lambda Not Invoked

Check Lambda permissions:

aws lambda get-policy --function-name MyFunction

Required permission:

{
  "Principal": "events.amazonaws.com",
  "Action": "lambda:InvokeFunction",
  "Resource": "function-arn",
  "Condition": {
    "ArnLike": {
      "AWS:SourceArn": "rule-arn"
    }
  }
}

Events Not Reaching Custom Bus

Check:

Publishing to correct bus name
Event format is valid JSON
Put events has proper permissions

# Test publish
aws events put-events \
  --entries '[{
    "Source": "test",
    "DetailType": "Test Event",
    "Detail": "{}",
    "EventBusName": "my-app-events"
  }]'

Viewing Failed Events

# Enable CloudWatch metrics
aws events put-rule \
  --name my-rule \
  --event-pattern '...' \
  --state ENABLED

# Check FailedInvocations metric
aws cloudwatch get-metric-statistics \
  --namespace AWS/Events \
  --metric-name FailedInvocations \
  --dimensions Name=RuleName,Value=my-rule \
  --start-time $(date -d '1 hour ago' -u +%Y-%m-%dT%H:%M:%SZ) \
  --end-time $(date -u +%Y-%m-%dT%H:%M:%SZ) \
  --period 300 \
  --statistics Sum

Rules

Event Patterns

Targets

Scheduler

Common Patterns

Create Custom Event Bus and Rule

Publish Custom Events

Scheduled Events

EventBridge Scheduler (One-Time and Flexible)

AWS Service Events

CLI Reference

Event Buses

Rules

Targets

Events

Best Practices

Event Design

Reliability

Security

Cost Optimization

Troubleshooting

Rule Not Triggering

Lambda Not Invoked

Events Not Reaching Custom Bus

Viewing Failed Events

References

eventbridge

AWS EventBridge

Table of Contents

Core Concepts

Event Bus