Using less information to make better decisions. In many large-scale web services, multiple layers of stateless and stateful services are seperated by load balancers. Load balancing can be done with dedicated hardware, with dedicated software load balancers, using DNS trickery or through a load-balancing mechanism in the client. In large systems, the resources and constraints at each layer can vary widely. Some layers are stateless, and easily scale horizontally to many machines. Other layers ma...