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The low down on SNS

The What –

Amazon Simple Notification Service (SNS) is a managed messaging service that Amazon Web Services (AWS) provides. It enables users to send messages or notifications in the form of topics to a distributed set of subscribers.

The Why –

1. Scalability: SNS is fully managed by AWS, meaning it can automatically handle scaling to send messages to many subscribers without any intervention. It can adapt to varying loads without any manual adjustments.
2. Versatility of Delivery Protocols: With SNS, you can send messages to many endpoints and protocols such as email, SMS, Application, Lambda functions, HTTP(s) endpoints, and even directly to other AWS services like SQS.
3. Reliability: AWS SNS offers robust delivery retries. If SNS cannot deliver a message to the endpoint, it will retry several times to ensure the message gets through. This provides higher delivery success rates.
4. Cost-Effective: With a pay-as-you-go pricing model, users pay only for what they use. There are no upfront costs or ongoing maintenance expenses. SNS offers a free tier, making it even more attractive for startups and developers.
5. Decoupling: In software architecture, especially in microservices or event-driven architectures, decoupling producers and consumers of messages is crucial. SNS can be used as an intermediary to decouple services, increasing the system’s resilience and maintainability.
6. Message Filtering: Subscribers can set filters to receive only specific messages of interest. This ensures that endpoints only process relevant messages, improving efficiency and cost savings.
7. Fanout Capability: A single message published to an SNS topic can trigger multiple actions. For instance, an event can simultaneously update a database, send a notification, and enqueue a message in SQS.
8. Security: AWS SNS integrates with AWS Identity and Access Management (IAM), allowing users to set permissions on who can publish or subscribe to a topic. SNS also supports message encryption, protecting data in transit and at rest.
9. Integrated with AWS Ecosystem: SNS seamlessly integrates with other AWS services, making it convenient for users who already rely on AWS for other aspects of their operations.
10. Global Reach with SMS: SNS allows sending SMS messages to over 200 countries. This is particularly beneficial for businesses with a worldwide user base.
11. Structured Message Formats: SNS supports structured message formats like JSON, allowing for richer and more actionable notifications.
12. Instantaneous Delivery: For real-time applications where immediacy is essential (e.g., critical alerts, live updates), SNS ensures notifications are delivered promptly.

The When –

1. Critical Alerts: Notify IT administrators, support teams, or users about crucial events, such as system failures, unusual activities, or outages.
2. Mobile Push Notifications: Deliver push notifications to mobile devices (iOS, Android, etc.) to inform users about updates, promotions, or other relevant news.
3. System Monitoring: Integrate with Amazon CloudWatch or other monitoring services to receive notifications when specific metrics breach their thresholds or when alarms are triggered.
4. Workflow Coordination: Notify downstream systems or services to perform specific tasks in multi-step processes, ensuring different microservices or application layers are notified of changes or events.
5. Transactional Emails: Send transactional emails to users, such as order confirmations, password reset links, or account activity alerts.
6. Content Distribution: Notify subscribers about new content or updates, like when a new blog post is published or new video content becomes available.
7. Fanout Messaging: Deliver a single message to multiple endpoints. For instance, you can simultaneously update a database, send an email, and enqueue a message in SQS with one published SNS message.
8. Decoupling Microservices: Use SNS combined with Amazon SQS to decouple services in a microservices architecture. This ensures that messages aren’t lost even if one service fails and can be processed when the service is available again.
9. Application Integration: Integrate disparate applications by using SNS as an event bus. When one application acts, it can publish a message to SNS, which other applications can respond to.
10. User Engagement and Retention: Send targeted messages or campaigns to engage users based on their behaviors, actions, or preferences.
11. Two-factor Authentication (2FA): Deliver SMS messages as part of a two-factor authentication system.
12. Data Replication: Notify systems to initiate data replication processes when new data is added or updates are made.
13. Public News Feed or Announcements: Use SNS to broadcast public messages or announcements, like product launches or company news.
14. Emergency Alerts: Send out emergency notifications, like weather warnings or safety alerts, to a broad audience across multiple channels (SMS, email, push notifications).
15. Consumer Device Updates: Notify consumer devices, like smart home gadgets, of firmware updates or status changes.

Example Reference Architectures –

Best practices for implementing event-driven architectures in your organization <1>

Figure 1. Topic fanout pattern based on Amazon SQS and Amazon SNS

Coordinating large messages across accounts and Regions with Amazon SNS and SQS <2>

Figure 2. Application coordination across accounts and a single AWS Region

1. Best practices for implementing event-driven architectures in your organization
2. Coordinating large messages across accounts and Regions with Amazon SNS and SQS