> For the complete documentation index, see [llms.txt](https://notes.radifine.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://notes.radifine.com/aws/other-aws-services/aws-messaging-services/aws-simple-queue-service-sqs.md).

# AWS Simple Queue Service (SQS)

Where AWS SNS lags is that it just passes messages, but cannot store the message for very long. This is where AWS Simple Queue Service comes into picture, where message can reside for upto 14 days.

It is also a fully managed service that is fully fault tolerant, meaning if something go down (such as power outages at the consumer end of the queue), because messages in queue can wait, it can be processed later.

SQS offers two types of queues:

* **Standard Queues**: These provide at-least-once delivery, meaning a message might be delivered multiple times **but is processed in no particular order**.
* **FIFO (First-In-First-Out) Queues**: These ensure that messages are processed exactly once and in the order they are sent.
* **Dead-Letter Queues:** If a message cannot be processed after a specified number of attempts, it can be sent to a dead-letter queue for further investigation and debugging.


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