Chapter 16: AWS SNS

AWS SNS — full name Amazon Simple Notification Service.

If you’ve been following our series, remember we discussed SQS (queues for reliable task processing), EventBridge (smart event routing), and now SNS fits right in as the broadcast king — perfect for fan-out scenarios where one message needs to reach many places quickly.

SNS is one of the oldest AWS services (launched 2010) but still hugely popular in 2026 for push notifications, alerts, and real-time pub/sub. It’s fully managed, serverless, and super simple to start with.

Let me explain it like we’re sitting together with a whiteboard — slow, with everyday analogies, Hyderabad/India examples, features, how it differs from others, pricing (2026 numbers), and a mini hands-on.

1. What is Amazon SNS? (Simple + Official Definition)

Amazon Simple Notification Service (SNS) is a fully managed pub/sub messaging service that enables you to send notifications (messages) from publishers to multiple subscribers instantly.

• Pub/Sub model (publish/subscribe):
  • Publisher sends a message to a topic (logical channel).
  • SNS pushes (fan-out) the message to all subscribers of that topic.
  • Subscribers don’t poll — SNS delivers push-style.
• Key idea: One publish → many deliveries (fan-out). Great for broadcasting the same info to different systems/users.

Official short line (from AWS docs 2026): “Amazon SNS is a web service that enables applications, end-users, and devices to instantly send and receive notifications from the cloud.”

In Hyderabad terms: Think of SNS as the loudspeaker at Charminar during festivals — one announcement (“Sale starts now!”) → reaches thousands of phones (SMS), emails, apps (push), backend services (Lambda/SQS), and even WhatsApp-like integrations — all at once, reliably.

2. Why Use SNS? (Core Benefits – Real Wins)

• Fan-out / Broadcasting → One message reaches many endpoints (decouples sender from receivers).
• Real-time push → No polling needed → faster & cheaper than constant checks.
• Multi-protocol delivery → Supports many endpoint types in one service.
• High throughput → Millions of messages/second, auto-scales.
• Reliability → Durable (messages stored briefly), retries on failure, dead-letter queues.
• Security → Encryption (at-rest & in-transit), IAM policies, VPC endpoints.
• Cost-effective → Pay-per-use, generous free tier.

Common use cases in India/Hyderabad:

• OTP/SMS alerts (banking, food delivery)
• Push notifications to mobile apps
• Alerting teams (monitoring, DevOps)
• Fan-out to microservices (order placed → notify inventory, email, analytics)

3. How SNS Works (Step-by-Step Flow)

1. Create a Topic → Standard (high throughput) or FIFO (ordered + deduplicated).
2. Publish a message to the topic (via console, SDK, API, or integration).
3. Subscribers subscribe to the topic (confirm subscription if needed).
4. SNS pushes the message to all confirmed subscribers.
5. If delivery fails → retries (exponential backoff) → optional dead-letter queue.

Message format: JSON/text up to 256 KB (most payloads fit).

4. Supported Endpoint Types (Where SNS Can Deliver)

Pro tip: Common pattern: SNS topic → multiple SQS queues + Lambda + SNS (for SMS) → full fan-out + buffering.

5. Standard vs FIFO Topics (Important Choice)

2026 note: FIFO improved batching & throughput — many use FIFO for payment flows.

6. Pricing in 2026 (Pay-as-you-go – From Official)

• Free Tier (monthly):
  • 1 million publishes/requests
  • 1 million mobile push notifications
  • 1,000 email notifications
  • Etc.
• Beyond free (ap-south-1 Mumbai region approx, USD → ~₹83–85):
  • Publishes/API requests: $0.50 per million (after free)
  • Deliveries:
    • Mobile push: $0.50 per million
    • HTTP/S: $0.60 per million
    • Email: $2.00 per 100,000
    • SMS: Varies by country (India ~$0.007–0.02 per SMS)
  • Data: $0.06 per GB delivery (rarely hits)

Example cost: 10,000 daily order alerts (SMS + push + Lambda) → often ₹500–2,000/month after free tier — very affordable.

7. Real Hyderabad Example: Food Delivery App

Your mini-Swiggy in Gachibowli:

• Order placed → backend publishes to SNS topic “order-updates”.
• SNS fans out to:
  • SMS to customer (“Order #123 confirmed!”)
  • Push to delivery partner app
  • Lambda to update inventory
  • SQS queue for analytics
  • Email receipt to user
  • Another SNS topic for restaurant partner

Result: One publish → 5+ actions in parallel → real-time, no blocking, scales during lunch rush.

8. Quick Hands-On (Free Tier – Try Now!)

1. Console.aws.amazon.com → SNS → Create topic “hyd-order-alerts” (Standard).
2. Subscribe your email + create SQS queue & subscribe it.
3. Publish test message: {“orderId”: “456”, “status”: “ready”}.
4. Check: Email arrives + message in SQS.

Cost? Usually ₹0.

Summary Table – SNS Cheat Sheet

SNS is the “shout it to everyone” service — pairs beautifully with SQS for fan-out + buffering, or EventBridge for smarter routing.

Got it? Next?

• SNS + SQS fan-out pattern deep dive?
• Mobile push notifications setup?
• SNS vs EventBridge detailed comparison?

Just say — next class ready! 🚀🔔