What is the purpose of the visibility timeout in AWS SQS?

The visibility timeout in Amazon Simple Queue Service (SQS) is a critical feature that plays a key role in message processing. Its primary purpose is to prevent other components or consumers from receiving and processing a message for a specified period of time after it has been retrieved from the queue. This time period allows the processing component (such as an application server) the opportunity to process the message without the risk of the same message being picked up and processed by another component simultaneously.

When a consumer retrieves a message from the SQS queue, the message becomes "invisible" to other consumers for the duration of the visibility timeout. If the message is processed successfully within that time frame, it can be deleted from the queue. However, if the processing fails or takes longer than the visibility timeout, the message will become visible again in the queue, allowing another component to attempt processing it.

This mechanism helps avoid duplicate processing and ensures that only one component can work on the message at a time. Hence, the visibility timeout is crucial for managing message consumption within applications that leverage SQS.