Unlocking Event-Driven Architectures with Amazon EventBridge

Introduction

As modern applications shift towards microservices and serverless architectures, decoupled systems and real-time event processing become critical. Enter Amazon EventBridge, AWS’s event bus service that connects application data from your services, integrated SaaS applications, and AWS services to enable real-time, event-driven workflows.

In this blog, we’ll take a technical deep dive into EventBridge, explore how it differs from SNS and SQS, examine its architecture, and build a simple event-driven pipeline to demonstrate its capabilities.

🧠 What is Amazon EventBridge?

Amazon EventBridge is a serverless event bus that makes it easy to connect applications using data from your own applications, integrated SaaS providers (like Auth0, Zendesk, Shopify), and AWS services.

It routes events based on rules to targets like Lambda, Step Functions, SQS, Kinesis, and more — without needing to write custom polling or filtering logic.

🔄 EventBridge vs SNS vs SQS

🏗️ Architecture: Under the Hood

An EventBridge setup consists of:

• Event Sources: AWS services, your apps, or SaaS apps.
• Event Bus: Default, Partner, or Custom.
• Rules: JSON pattern-based filters.
• Targets: AWS services like Lambda, SQS, Step Functions, or even HTTP APIs.

You send events to a bus, which evaluates them against rules and sends them to matched targets.

🛠️ Hands-On: Building an Event-Driven Workflow

Scenario

You have an e-commerce app. When a new order is placed (via a Lambda function), an event is published to EventBridge. Based on that event, EventBridge triggers:

1. A Lambda to update inventory.
2. A Step Function to initiate fulfillment.
3. Sends the event to an SQS queue for async analytics processing.

Step 1: Define the Event Schema

{
  "source": "custom.ecommerce",
  "detail-type": "OrderPlaced",
  "detail": {
    "orderId": "1234",
    "items": ["sku-1", "sku-2"],
    "total": 49.99
  }
}

Step 2: Create a Custom Event Bus

aws events create-event-bus --name ecommerce-bus

Step 3: Add a Rule to Route Events

event-rule.json

{
  "Source": ["custom.ecommerce"],
  "DetailType": ["OrderPlaced"]
}

aws events put-rule \
  --name OrderPlacedRule \
  --event-bus-name ecommerce-bus \
  --event-pattern file://event-rule.json

Step 4: Add Targets

aws events put-targets \
  --rule OrderPlacedRule \
  --event-bus-name ecommerce-bus \
  --targets file://targets.json

targets.json

[
  {
    "Id": "InventoryLambda",
    "Arn": "arn:aws:lambda:us-east-1:123456789012:function:UpdateInventory"
  },
  {
    "Id": "FulfillmentStepFunction",
    "Arn": "arn:aws:states:us-east-1:123456789012:stateMachine:FulfillOrder"
  },
  {
    "Id": "AnalyticsQueue",
    "Arn": "arn:aws:sqs:us-east-1:123456789012:analytics-queue"
  }
]

Step 5: Send a Test Event

aws events put-events --entries file://event.json

event.json

[
  {
    "Source": "custom.ecommerce",
    "DetailType": "OrderPlaced",
    "Detail": "{\"orderId\": \"1234\", \"items\": [\"sku-1\", \"sku-2\"], \"total\": 49.99}",
    "EventBusName": "ecommerce-bus"
  }
]

✅ Key Benefits

• Loose coupling between producers and consumers
• Schema Registry and schema discovery
• Native support for SaaS and AWS integrations
• Scalability and durability with at-least-once delivery

🔐 Best Practices

• Use custom event buses to isolate domains
• Implement dead-letter queues (DLQs) to handle failures
• Leverage schema validation to prevent malformed events
• Use event replay to reprocess past events (available via Archive & Replay)

Conclusion

Amazon EventBridge is a cornerstone for building resilient, scalable, event-driven applications in AWS. Whether you’re decoupling microservices, responding to external triggers, or handling complex workflows, EventBridge offers a clean, powerful, and highly integrative approach.

If you’re not already using it in your architecture, now’s the time to consider where EventBridge can help simplify your systems.