What is Layer 7 load balancing?
Layer 7 is the application layer. When performing layer 7 load balancing, the load balancer has more information with which to make load balancing related decisions since more information about upper level protocols is available.
Layer 7 load balancing uses a proxy at the application layer (HAProxy). Requests are terminated on the load balancer, and the proxy generates a new request which is passed to the chosen Real Server.