AWS SNS Pub/Sub Messaging

Publish/subscribe fan-out to SQS, Lambda, HTTP, email, and mobile push endpoints.

AWSIntermediate

Why

SNS fans out one event to many subscribers — decoupling producers from N consumers. 1M publishes/mo free. Pairs with SQS for durable fan-out (SNS → SQS → Lambda).

When

Use for event fan-out (order placed → email + analytics + inventory), system events, and mobile push. Avoid for point-to-point (use SQS).

How

1. Create topic — aws sns create-topic --name my-topic 2. Subscribe — aws sns subscribe --topic-arn ... --protocol sqs --notification-endpoint <queue-arn> 3. Publish — aws sns publish --topic-arn ... --message '{"event":"order"}' 4. Fan-out — one topic, many SQS subscriptions, each gets copy 5. Filtering — subscription filter policy, only matching messages delivered 6. FIFO topic — .fifo, preserves order within message group 7. DLQ — per-subscription, captures delivery failures 8. Cross-account — subscribe with proper IAM policy

Example

# Fan-out: SNS → 3 SQS queues aws sns create-topic --name order-events TOPIC_ARN=arn:aws:sns:us-east-1:123:order-events for queue in email analytics inventory; do Q_ARN=$(aws sqs create-queue --queue-name $queue --query QueueUrl --output text) aws sns subscribe --topic-arn $TOPIC_ARN \ --protocol sqs --notification-endpoint $Q_ARN \ --attributes RawMessageDelivery=true done # Publish event to all subscribers aws sns publish --topic-arn $TOPIC_ARN \ --message '{"orderId":"456","total":99.99}'

Common Problems

⚠SQS subscription needs policy — SNS must have sqs:SendMessage on the queue
⚠No message ordering in Standard topic — use FIFO topic + FIFO queues
⚠Cross-account subscription fails — queue policy must allow publisher account

Best Practices

✓Use SNS → SQS → Lambda pattern — SQS buffers, handles retries, Lambda scales
✓Filter policies per subscription — only deliver relevant messages, cuts cost
✓Enable RawMessageDelivery — cleaner JSON in SQS, no SNS envelope wrapper

FAQ

What is AWS SNS Pub/Sub Messaging and what problem does it solve?

Publish/subscribe fan-out to SQS, Lambda, HTTP, email, and mobile push endpoints. It lets developers deploy, store, and scale without self-managing infrastructure — a core reference for cloud service selection.

How do I get started with AWS SNS Pub/Sub Messaging in 5 minutes?

Two steps to run it: (1) Create topic — aws sns create-topic --name my-topic; (2) Subscribe — aws sns subscribe --topic-arn ... --protocol sqs --notification-endpoint <queue-arn>. Validate on the free tier first, then wire into production.

What is the #1 pitfall with AWS SNS Pub/Sub Messaging?

The most frequent issue is: SQS subscription needs policy — SNS must have sqs:SendMessage on the queue. Run a pre-launch checklist item by item, and add policy/config scanning in CI.

What are the best practices for AWS SNS Pub/Sub Messaging?

Best practices for AWS SNS Pub/Sub Messaging include: Use SNS → SQS → Lambda pattern — SQS buffers, handles retries, Lambda scales; Filter policies per subscription — only deliver relevant messages, cuts cost; Enable RawMessageDelivery — cleaner JSON in SQS, no SNS envelope wrapper. The first one — "Use SNS → SQS → Lambda pattern — SQS buffers, handles retries, Lambda scales" — should be a team default baked into your IaC templates.

How do I control cost and avoid bill surprises with AWS SNS Pub/Sub Messaging?

Three ways to prevent overspend: (1) tag every resource with env/team and enable billing alarms; (2) set budget thresholds to trigger Slack/email alerts; (3) review idle resources in Cost Explorer regularly and clean them up. Most AWS SNS Pub/Sub Messaging options offer a free tier — validate within free quota before scaling.