Hey @nizaeros! I think I found a solution for you - can you try using this CDN instead: https://cdnjs.cloudflare.com/ajax/libs/aws-sdk/2.1664.0/aws-sdk.min.js? I tried it out on a Cloud instance and it seems to work. The only potential issue is that its version isn't recent enough, but it seems to support CloudFront. 
In general, we recommend searching for minified CDNs on cdnjs, as they seem to have the greatest compatibility with Retool's custom libraries functionality.
I hope that helps! Don't hesitate to follow up here if you run into any other issues.