CFEngine operates autonomously in a network, under your guidance. While CFEngine supports anything from 1 servers to 100,000+ servers, the essence of any CFEngine deployment is the same.
CFEngine supports networks of any size, from a handful of nodes to hundreds of thousands of computers. It is built to scale. If your site is very large (thousands or of servers) you should spend some time discussing your requirements with the CFEngine experts. They will know how to tune promises and configurations to your environment as scale requires you to have more infrastructure, and a potentially more complicated configuration.
But no matter the scale, the essence of any CFEngine deployment is the same.