Signature expired: is now earlier than error : InvalidSignatureException

Question

I am trying a small example with AWS API Gateway and IAM authorization. The AWS API Gateway generated the below Endpoint :

https://xyz1234.execute-api.us-e         


        

Answer 1

Complementing what as @miked-at-aws post about AWS sigV4, There are at least 2 main possible route causes for the clock skew:

1. your CPU is overloaded (reaching 99% usage or in EC2 instances with CPU limits that run out on CPU credits).

Why would this generate the time skew? because when the amazon SDK creates the time stamp to the moment the request is sent, normally there shouldn't be more than just a few nano or micro seconds, but if your CPU is overwhelmed it may take it several seconds or even minutes in some cases to process, so for this root cause you will experience not a 100% events lost but just some x% that may not be too big.

2. for the second root cause which is that your machine clock isn't just adjusted, well probably 100% of your events are being lost and you just have to make sure that your machine clock is being set and adjusted correctly.