At GitHub we serve billions of HTTP, Git and SSH connections each day. To get the best performance we run on bare metal hardware. Historically one of the more complex components has been our load balancing tier. Traditionally we scaled this vertically, running a small set of very large machines running haproxy, and using a very specific hardware configuration allowing dedicated 10G link failover. Eventually we needed a solution that was scalable and we set out to create a load balancer solution that would run on commodity hardware in our typical data center configuration.