I am creating a web service of scheduled posts to some soc. network.
Need help dealing with file uploads under high traffic.

Process overview:

• User uploads files to SomeServer (not mine).
• SomeServer then responds with a JSON string.
• My web app should store that JSON response.

Opt. 1 — Save, cURL POST, delete tmp
The stupid way I made it work:

1. User uploads files to MyWebApp;
2. MyWebApp cURL's the file further to SomeServer, getting the response.

Opt.2 — JS magic
The smart way it could be perfect:

1. User uploads the file directly to SomeServer, from within an iFrame;
2. MyWebApp gets the response through JavaScript.

But this is(?) impossible due to the 'Same Origin Policy', isn't it?

Opt. 3 — nginx proxying?
The better way for a production server:

1. User uploads files to MyWebApp;
2. nginx intercepts the file uploads and sends them directly to the SomeServer;
3. JSON response is also intercepted by nginx and processed by MyWebApp.

Does this make any sense, and what would be the nginx config for, say, /fileupload Location to proxy it to SomeServer ?