Application Integration
Amazon SNS
Pub/sub messaging and fan-out
Amazon SNS is a managed publish/subscribe service that fans messages out to many subscribers (SQS queues, Lambda, HTTP endpoints, email, SMS). The SNS→SQS fan-out pattern gives each consumer its own durable queue.
When to use it
- Broadcasting an event to many independent consumers
- Triggering parallel workflows from a single event
- Push notifications, email, SMS alerts
When NOT to use it
- Guaranteed per-consumer processing semantics without pairing with SQS
- Strictly ordered message processing (SNS FIFO topics exist for some cases; SQS FIFO is the usual answer)
Key exam points
- Pub/sub: one message → many subscribers; producer unaware of consumers
- Fan-out pattern: SNS topic → per-consumer SQS queues
- Message filtering lets subscribers receive only relevant messages
Compared with
- Amazon SQS — SQS delivers each message to one consumer; SNS delivers each message to every subscriber.