Why you need this?You don’t want your heavy-weight data to travel 2 legs from Client to Server to S3, incurring the cost of IO and clogging the pipe 2 times. Instead, you want to ask your server to give your client one-time permission to upload your data directly to S3. The process is still 2 legged, but heawy-weight data travels only on 1 leg. On Amazon S3 this is implemented with CORS (Cross Ori