Excel files on S3 can be connected through REST API. For this connection to happen the signed portions (using AWS Signatures) of requests are valid within 15 minutes of the timestamp in the request to maximize protection by signing request headers and body as AWS requires that all API requests be signed. The signing process helps protect message integrity by preventing tampering with the request while it is in transit, it also helps protect against potential replay attacks.
Thus, if this requirement is mandatory and is requested by AWS then denodo authentication information sent in a request must include a “signature”. If a request is not reached to AWS within 15 minutes of the time stamp then it will deny it.
Hope this helps!