mongoose/docs/c-api/mg_http_server.h/mg_http_reverse_proxy.md

title	decl_name	symbol_kind	signature
mg_http_reverse_proxy()	mg_http_reverse_proxy	func	void mg_http_reverse_proxy(struct mg_connection *nc, const struct http_message *hm, struct mg_str mount, struct mg_str upstream);

Proxies a given request to a given upstream http server. The path prefix in mount will be stripped of the path requested to the upstream server, e.g. if mount is /api and upstream is http://localhost:8001/foo then an incoming request to /api/bar will cause a request to http://localhost:8001/foo/bar

EXPERIMENTAL API. Please use http_serve_http + url_rewrites if a static mapping is good enough.