Amazon SQS
SNS + SQS Fan-out
Broadcast one event to many independent queues by combining a topic with subscriber queues.
SQS queues are point-to-point: each message is processed by one consumer of that queue. To deliver the same event to multiple independent subscribers, you put Amazon SNS (a pub/sub topic) in front and subscribe several SQS queues to it. A single publish to the SNS topic is fanned out to every subscribed queue, each of which is consumed independently by its own service.
A press release (SNS publish) sent to a distribution list: every news outlet (SQS queue) gets its own copy in its own inbox and acts on it independently and at its own pace, while you the sender only sent it once.
Key Concepts
1
This decouples producers from a growing set of consumers: adding a new subscriber is just subscribing a new queue to the topic, no producer change. Each queue gets its own copy, its own retry/visibility behaviour, and its own DLQ, so a slow or failing subscriber never affects the others. SNS message filtering lets each subscription receive only the subset of messages matching attribute filters.
2
For ordered fan-out, SNS FIFO topics deliver to SQS FIFO queues while preserving order and deduplication.