Forgive me for not fully understanding this. If I'm just using proxy_pass to a single server (vs using proxy_pass with round robin or using proxy_next_upstream

Forgive me for not fully understanding this. If I'm just using proxy_pass to a single server (vs using proxy_pass with round robin or using proxy_next_upstream for failover) would this still affect me? In my experience with proxy_pass, a timeout on upstream was reported to the client and the POST was not retried.