Reverse proxy for upload

[Marcin Wanat]

Hi,

i am working on nginx reverse proxy for upload gateway to speed up
things worldwide.
Infrastructure schema looks like this:

Main upload server - EU
Upload proxy servers in Asia, Australia, North America etc

Upload proxy servers will be connected to main upload servers via Long
Fat Network VPN - 10Gbps, but large RTT (located on different
continents)

Client will be sending 10GB+ files splitted to multiple 10MB POST
requests with data. Local nginx proxy server should read (buffer) this
request as soon as possible and immediately reply with HTTP 200, even
before it will finish proxying the request to upstream. We can reply
HTTP 200 before transmitted to upstream because we do not care about
data consistency here, as client will verify checksum with master
upload server after last piece and then resend missing pieces if
anything goes wrong. We are optimizing for speed only here.

My question is - is it possible with nginx that proxy server will
reply to client with HTTP 200 before request is fully transmitted to
upstream?

Regards,
Marcin