Amazon Simple Notification Service (SNS)
- What it is
- Simple Notification Service — fully managed publish/subscribe (pub/sub) messaging.
- A publisher sends one message to a topic; SNS pushes it to every subscriber.
- Model: one-to-many, push-based
- Subscribers: Amazon Simple Queue Service (SQS) queues, AWS Lambda functions, HTTP/S endpoints, email, SMS, mobile push.
- Message is delivered immediately; there is no queue for a subscriber to catch up from later.
- Fan-out pattern
- SNS topic → several SQS queues. Combines broadcast delivery with durable, retryable processing. Classic exam answer.
- Not to be confused with
- SQS — pull-based, one consumer per message, durable buffer.
- Amazon Simple Email Service (SES) — bulk/transactional email at scale with templates and deliverability tooling. SNS email is for simple system alerts.
- Exam signal
- “Send alerts/notifications to many recipients” → SNS.