Amazon EventBridge | Overview.

Amazon EventBridge - Overview.

Scope:

• Intro,
• Core Concepts,
• Key Benefits,
• Link to official documentation,
• Insights.

Intro:

• Amazon EventBridge is a serverless event bus service that enables twtech to build event-driven applications at scale using events from its applications, third-party software as a service (SaaS) applications, and other AWS services. 
• Amazon EventBridge provides a simple, consistent way to ingest, filter, transform, and deliver events to various targets for processing. 

Core Concepts

• Events: An event signifies a change in an environment or system, such as an object being added to an Amazon S3 bucket or a change in an EC2 instance's state.
• Event Buses: Event buses act as routers that receive events and deliver them to specified targets.
• Rules: Rules define what EventBridge does with the events delivered to an event bus. There are two types:
• Event Patterns: Rules that match specific data patterns within an event's structure.
• Schedules: Rules that run on a predefined schedule (e.g., using cron expressions) to invoke targets at specific times.
• Targets: When an event matches a rule, EventBridge sends the event's JSON message to one or more designated targets, such as AWS Lambda functions, Amazon SNS topics, Amazon SQS queues, or API destinations. 

Key Benefits

• Decoupling: EventBridge allows for the decoupling of application components, making the system more resilient and easier to maintain.
• Integration: It simplifies integration with a wide array of AWS services and SaaS partners without requiring custom code.
• Scalability and Reliability: The service is designed for low-latency, high-throughput event processing and offers high reliability for event delivery.
• Content-Based Filtering: It supports precise filtering using comparison operators and ranges of values within the event data, reducing the need for downstream custom filtering logic. 

Link to official documentation:

 Amazon EventBridge documentation.

https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-what-is.html

twtech-Insights:

1. What EventBridge Really Is

Amazon EventBridge is a serverless event bus that enables event-driven architectures by routing events from producers to consumers using rules.

Think of it as:

A smart event router with schema awareness and SaaS integrations

It evolved from CloudWatch Events, but now supports:

• Multiple event buses
• Cross-account routing
• Schema registry
• SaaS event sources (e.g., Salesforce, Zendesk)
• Fine-grained filtering & transformations

2. Core Architecture Components

 Event Sources (Where events originate from).

Types:

• AWS Services
  EC2, S3, Lambda, ECS, Step Functions, CodePipeline, etc.

• Custom Applications
  Via PutEvents API

• SaaS Partners
  (Stripe, Auth0, Datadog, PagerDuty, etc.)

NB:

Each event is a JSON document.

 Event Bus

A logical container for events.

Three types:

1. Default Event Bus

   • Automatically receives AWS service events

2. Custom Event Bus

   • For application-specific or domain-driven architectures

3. Partner Event Bus

   • Dedicated to SaaS integrations

 Best Practice:

• Use one event bus per domain (e.g., orders-bus, billing-bus)

 Events (Structure)

• An EventBridge event has a predictable shape:

{
  "source": "aws.ec2",
  "detail-type": "EC2 Instance State-change Notification",
  "time": "2026-01-27T10:15:30Z",
  "region": "us-east-2",
  "resources": [],
  "detail": {
    "instance-id": "i-1234567890",
    "state": "running"
  }
}

Key fields:

• source → Who emitted the event
• detail-type → What kind of event it is
• detail → The payload you actually care about

 Rules

• Rules decide which events go where.

Each rule has:

• Event pattern (filter)
• Target(s)

Event Pattern Sample

{
  "source": ["aws.ec2"],
  "detail": {
    "state": ["stopped"]
  }
}

NB:

✔ Only matches EC2 stop events

✘ No code needed

 Targets

• Where matched events are delivered.

Common targets:

• AWS Lambda
• Step Functions
• SNS / SQS
• Kinesis Data Streams
• ECS tasks
• API Destinations (HTTP endpoints)

NB:

• 🎯 One rule → multiple targets allowed

3. Event Flow (End-to-End)

Event Source
   ↓
Event Bus
   ↓
Event Rule (Pattern Matching)
   ↓
Target(s)

Key characteristics:

• Push-based (no polling)
• Fully managed
• Near real-time (typically milliseconds)

4. Advanced Features (Where EventBridge Shines)

⭐ Schema Registry

• Automatically discovers event schemas
• Generates code bindings (Java, Python, TS)
• Helps teams avoid breaking changes

NB:

• 💡 Great for large orgs with multiple producers/consumers

 Event Transformations (Modify events without Lambda Sample):

{
  "instanceId": "$.detail.instance-id",
  "state": "$.detail.state"
}

This approach Reduces:

• Lambda glue code
• Cost
• Latency

 Cross-Account Event Routing

• EventBridge supports resource-based policies.

Use cases:

• Centralized monitoring account
• Security event aggregation
• Multi-account microservices

 Archive & Replay

• Store events for debugging or backfills
• Replay historical events to rules

This is for:

• Disaster recovery
• Reprocessing failed logic
• Auditing

5. Reliability, Limits & Guarantees

Delivery Guarantees

• At-least-once delivery
• Possible duplicates → consumers must be idempotent

Retry & DLQ

• Automatic retries
• Dead-letter queues (SQS or SNS)

Quotas (High level)

• 10,000 rules per bus (soft limit)
• Event size ≤ 256 KB
• ~100K events/sec per bus (region-dependent)

6. EventBridge vs Alternatives

Service	Best For
EventBridge	Event routing, SaaS integration, decoupling
SNS	Fan-out notifications
SQS	Durable message queues
Kinesis	High-throughput streaming
Kafka	Complex streaming & ordering

NB:

•  EventBridge is not a stream processor
•  It’s an event router & integration layer

7. Common Design Patterns

 Event-Driven Microservices

• Producers emit domain events
• Consumers subscribe independently
• Zero coupling

 Automation & Ops

• React to AWS service events
• Trigger remediation workflows

 SaaS Integration

• Receive third-party events
• Route internally without custom polling

 Choreography (vs Orchestration)

• EventBridge for loose coupling
• Step Functions when control flow matters

8. Security & IAM Model

• IAM controls PutEvents
• Resource policies control cross-account access
• Targets assume execution roles

🔐 Always:

• Restrict PutEvents
• Validate event source
• Use least privilege

9. Cost Model (Simple & Predictable)

• Charged per event published
• Free tier included
• No charge for rules or targets

NB:

• 💡 Cheaper than Lambda glue for routing logic

10. When NOT to Use EventBridge (Avoid it if twtech needs):

• Strict ordering
• Exactly-once delivery
• Massive streaming analytics
• Stateful processing