Complete procedures with a way back.

Trace one request from NGINX to the selected upstream and distinguish connection refusal, timeout, DNS, Unix-socket access, protocol mismatch, and invalid responses.

Proxy a private application through Apache with explicit timeouts, forwarded headers, WebSocket upgrades, health checks, and no accidental forward-proxy exposure.

Balance requests across private backends, set explicit connect/read timeouts, use passive health behavior, preserve client context, and rehearse one-node failure.