You can do TCP proxying with nginx but many of the same features available in haproxy are behind the paywall. In nginx, layer 4 connections are dealt with through streams. You can do both TCP and UDP. I stick with haproxy for TCP streams with very few exceptions. HAproxy is most definitely more robust for situations where you have a pool of upstream servers. For single upstream instances, it’s not terrible. Most of the features I would use for better control of how the failover and balancing would work isn’t available in the open source nginx.