Sounds like you are trying to push the file vs downloading it? I could be wrong, but I though presigned_url was only for getting a download link, maybe you need to use presigned_post?
For uploading files I’ve used put_object, i.e.
local_file = File.read!(src_path)
ExAws.S3.put_object(@bucket, dest_path, local_file)
|> ExAws.request!()
I don’t know if that will be of us to you however, given you are using react on the frontend.
