At scale yes. They're built to solve different problems and excel at each individually. Nginx can proxy, but HAProxy is more flexible. Nginx can cache, but Varn

At scale yes. They're built to solve different problems and excel at each individually. Nginx can proxy, but HAProxy is more flexible. Nginx can cache, but Varnish is much more flexible and efficient. We use all three technologies and route the traffic to the service best suited for the traffic.