AWS Messaging Services: SQS, SNS, and EventBridge

Introduction

• Topic: Differences between SQS, SNS, and EventBridge
• Agenda:
  1. Explanation of SQS, SNS, and EventBridge through examples
  2. Feature comparison and usage guidelines

SQS (Simple Queue Service)

• Overview: Old AWS service for reliable asynchronous communication.
• Main Concepts:
  • Queues: Temporary holding pools for messages, published by applications.
  • Messages: Can contain any data, usually JSON blobs with size limits.
  • Polling: Mechanism by which applications retrieve and process messages from the queue.
• Example: E-commerce order processing
  • Order Service: Publishes messages about order states to an Orders Analytics Queue.
  • Analytics Service: Pulls messages from the queue and processes them.
  • Integration with Lambda: SQS automatically polls the queue.
• Key Features:
  • Decouples services by publishing to a queue.
  • FIFO queues are available for ordered message processing.
  • Limits on message size.

SNS (Simple Notification Service)

• Overview: Pub/Sub model for high throughput and fan-out scenarios.
• Main Concepts:
  • Topics: Not holding pools; created with specific themes like “orders”.
  • Messages: JSON blobs with size limits.
  • Publish/Subscribe: Publishers send messages to a topic; subscribers receive a copy.
• Example: Multiple services (Accounting, Analytics, Dashboard) receiving order updates
  • Order Service: Publishes to an Orders Topic.
  • Services are subscribed to the topic and receive copies of messages.
  • Use of queues in front of services recommended for reliability.
• Key Features:
  • High throughput, ability to scale with millions of subscribers.
  • Decouples higher-order services from downstream processes.
  • Supports many-to-many communication.

EventBridge

• Overview: Newer service with additional functionality over SNS.
• Main Concepts:
  • Message Bus: Similar to topics, used to receive and send events.
  • Events: Generated by applications or AWS services, can integrate with 3rd-party SaaS.
  • Rules: Define which events are sent to which targets.
  • Targets: Endpoints that process events.
• Key Features:
  • Supports third-party integrations and AWS service events.
  • Message filtering available.
  • Limited to 5 targets per rule, which can be restrictive.

When to Use Which Service

• SQS:
  • Reliable one-to-one asynchronous communication.
  • Holds messages temporarily, allowing for back pressure and ordered processing if needed.
• SNS:
  • Ideal for one-to-many fan-out scenarios.
  • High throughput and many subscribers.
• EventBridge:
  • One-to-many with more flexibility; ideal for service and SaaS integrations.
  • Limited by the 5 targets per rule constraint.

Conclusion

• SQS, SNS, and EventBridge solve different problems despite their similarities.
• SQS is useful for message decoupling and ordered processing.
• SNS is ideal for high throughput and multiple subscribers.
• EventBridge shines in AWS service and third-party integrations but has a target limit.

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