How does Amazon SQS allow multiple readers to access the same message queue without losing messages or
processing them many times?

A.
By identifying a user by his unique id

B.
By using unique cryptography

C.
Amazon SQS queue has a configurable visibility timeout

D.
Multiple readers can’t access the same message queue

Explanation:
Every Amazon SQS queue has a configurable visibility timeout. For the designated amount of time after a message is
read from a queue, it will not be visible to any other reader. As long as the amount of time that it takes to process the
message is less than the visibility timeout, every message will be processed and deleted. In the event that the component
processing the message fails or becomes unavailable, the message will again become visible to any component reading
the queue once the visibility timeout ends. This allows you to have many components all reading messages from the
same queue, with each working to process different messages.
https://aws.amazon.com/sqs/faqs/