SNS and Fan-out Architecture

Overview of Amazon Simple Notification Service (SNS)

Amazon SNS is a simple yet powerful service that enables publish/subscribe (Pub/Sub) design patterns in cloud architecture. At its core, SNS facilitates message delivery from publishers to subscribers through topics.

This architecture is particularly valuable when you need multiple processes to react to the same event independently and concurrently.

Core Components

Topics

A topic serves as a communication channel for publishing notifications.

Subscriptions

Subscriptions configure endpoints to receive messages published to a topic. SNS supports multiple endpoint types:

• HTTP/HTTPS endpoints

• Email addresses

• SMS (text messages)

• Amazon SQS queues

• Amazon Device Messaging (ADM) for push notifications

• AWS Lambda functions

Fan-out Architecture Pattern

One of the most powerful design patterns enabled by SNS is the fan-out architecture, which is particularly useful for parallel processing workflows.

Example: Image Upload Processing

Consider a scenario where a user uploads an image. Here's how a fan-out architecture processes this event:

1. The image upload event is published to an SNS topic

2. Multiple subscribers process the event simultaneously:

   • Amazon Simple Email Service (SES) sends a thank-you note to the user

   • Amazon SQS queues the image for resizing by EC2 worker instances

   • AWS Lambda runs image analytics

Benefits

The fan-out architecture pattern through SNS offers several advantages:

• Enables parallel processing of the same event

• Creates loosely coupled system components

• Provides flexibility in adding or removing processing steps

• Improves system scalability and maintainability