We use HAProxy to load balance between our webservers. It balances TCP between the machines round robin and leaves everything else to Node.js, leaving the connections open with a reasonably long time to live to support WebSockets and re-use of a TCP connection for AJAX polling.

HAProxy manages internal and origin load balancing using KeepaliveD. Two small servers host the entire site, never moving about 15% load even during the largest load spikes.

We use HAProxy to balance traffic at various points in our stack, includgin nginx nodes on different physical machines, and api nodes on the backend.

I use HAproxy primarily for application routing and SSL termination. I also use its logs and statistics to visualize incoming traffic in Kibana.

We use HAProxy to load balance web requests for our web application, but also for some internal load balancing of microservices.