Introduction
Event-driven architecture (EDA) is a powerful pattern that enables decoupled communication between services, making applications more scalable, resilient, and extensible. AWS provides several services to implement EDA, with Amazon SNS, Amazon SQS, and Amazon EventBridge being the primary options. But when should you use each?
In this article, we'll break down their use cases, differences, and best practices to help you make the right choice for your architecture.
Amazon SNS (Simple Notification Service)
Best for: Real-time fan-out messaging (pub/sub)
Key Features:
- Push-based messaging: Instantly notifies multiple subscribers.
- Multiple subscriber types: Supports AWS Lambda, SQS, HTTP(S), email, SMS, and mobile push notifications.
- High throughput: Can handle millions of messages per second.
- Message filtering: Subscribers receive only relevant messages using attributes.
When to Use SNS:
- Broadcasting events to multiple downstream services in real-time (e.g., order confirmations to email, SMS, and analytics pipelines).
- Push notifications to applications and mobile devices.
- Triggering Lambda functions to process events asynchronously.
SNS Example Architecture:
Event Source → SNS Topic → (SQS | Lambda | Email | Mobile Push)
Amazon SQS (Simple Queue Service)
Best for: Decoupling services with reliable message queuing
Key Features:
- Pull-based messaging: Messages are stored until consumers process them.
- Multiple consumers: Allows parallel processing.
- Dead-letter queues (DLQ): Handles failed message processing.
- FIFO Queues: Guarantees order and exactly-once delivery (if required).
When to Use SQS:
- Decoupling microservices to avoid direct dependencies.
- Reliable message delivery when processing failures must be handled (e.g., payment processing, inventory updates).
- Load balancing for background jobs that require worker scaling.
SQS Example Architecture:
Event Producer → SQS Queue → Consumer Services (EC2, Lambda, ECS, etc.)
Amazon EventBridge
Best for: Advanced event routing and third-party integrations
Key Features:
- Event-driven routing: Uses rules to deliver events to the right target.
- Native AWS integration: Works with over 200 AWS services.
- Schema registry: Standardizes event formats for easy discovery.
- Supports SaaS integrations: Connects AWS with external applications like Datadog, Zendesk, and PagerDuty.
When to Use EventBridge:
- Cross-account or cross-service event routing (e.g., triggering workflows across AWS accounts).
- Connecting AWS with external SaaS applications (e.g., Salesforce, Zendesk integrations).
- Building loosely coupled microservices that rely on event buses instead of direct dependencies.
EventBridge Example Architecture:
AWS Service/SaaS App → EventBridge Event Bus → (Lambda | SQS | SNS | Step Functions)
SNS vs. SQS vs. EventBridge: Quick Comparison
| Feature | SNS | SQS | EventBridge |
|---|---|---|---|
| Message Delivery | Push | Pull | Push |
| Use Case | Pub/Sub | Queueing | Event Routing |
| AWS Integrations | Lambda, SQS, HTTP | EC2, Lambda, ECS | 200+ AWS Services |
| External SaaS Support | No | No | Yes |
| Message Order | No guarantee | FIFO available | No guarantee |
Choosing the Right Service
Use SNS if:
✔️ You need real-time notifications and fan-out messaging.
✔️ You want multiple subscribers receiving the same message simultaneously.
✔️ You don’t need message retention.
Use SQS if:
✔️ You need to decouple services and allow asynchronous processing.
✔️ You require message durability and retries.
✔️ You want exactly-once processing (FIFO queues).
Use EventBridge if:
✔️ You need a fully managed event bus for event routing.
✔️ You want to integrate AWS services with third-party SaaS applications.
✔️ You need dynamic event filtering and rule-based processing.
Conclusion
Amazon SNS, SQS, and EventBridge each serve distinct roles in event-driven architectures. SNS is ideal for real-time pub/sub messaging, SQS provides robust message queuing for decoupling services, and EventBridge offers advanced event routing with AWS-native and third-party integrations.
Choosing the right tool depends on your architectural needs—understanding their differences will help you design scalable, event-driven applications on AWS.
Have you used these services in your projects? Share your experiences in the comments! 🚀
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