Hi,

this has driven me crazy for hours. In your current implementation of S3 file upload, you are using Knox.

From Knox docs:

https://github.com/Automattic/knox#region

I think you should put this as a warning in the given example, as I've almost gone crazy. Knox.putFile was returning no error, but when fetched the res object, status code was 400 (bad request). After some investigations I came to the knox documentations. I was using eu-central-1 and file can't be uploaded to that region wit hthe current knox implementation.