Which characteristic is a key feature of Amazon SQS?

Amazon Simple Queue Service (SQS) is designed to provide a message queuing service that is highly scalable and reliable. One of its key features is that messages are stored redundantly across multiple servers. This ensures data durability and availability, as the likelihood of data loss is significantly reduced due to this redundancy. In the case of a server failure, another server can provide the message, allowing for uninterrupted message processing.

The other choices present characteristics that do not accurately represent SQS's capabilities. For example, message retention can actually last from a few seconds up to 14 days, far exceeding a limit of just 2 days. Additionally, messages can be processed outside of a 30-minute window; in fact, SQS allows for longer processing times than this. The option suggesting that only one consumer can process a message is also misleading; SQS supports a distributed system where multiple consumers can poll and process messages concurrently, enhancing the throughput of the message processing system.

Thus, the storage of messages across multiple servers is a foundational characteristic that underscores the reliability and effectiveness of Amazon SQS, allowing it to serve as a robust solution for decoupling microservices and managing asynchronous communication in cloud applications.