I am trying to address the following use case :
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* A 'post request' is send to Nginx which forward it to a first upstream server "upstream 1". "upstream 1" is in charge of authenticating the request origin, and do some accounting in order to determine if the request can be authorized ...
* If OK, we would like to terminate processing the request at "upstream 2"

What we have briefly tried :
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* internal redirect ( using x-accel-redirect) to "upstream 2"
* how could we possibly "post" to this second "upstream 2" ?

Thank you for your help