"The inside of a computer is as dumb as hell but it goes like mad!"—Richard Feynman
Back in the day, the way to speed up slow web servers was to add more cores. I recall one employer buying a monster 24-core Sun box the size of a Hummer. We had to have the data center door widened to get it in.
Scaling websites nowadays is still a matter of adding cores, but they either come in their own little beige boxes, as commodity hardware, or you rent them as as a wholesale compute resource from a cloud provider. In order to group all these cores together to serve a single website, we use load balancers.
Once, a load balancer was a big box that sat in a rack and cost eighty thousand dollars. Although you ...