[flatline3]

> Or are they just serving up web pages to users? That's RAM and bandwidth heavy, but very CPU light. You still need the machines to scale your load, but you're not going to be using the CPU.

That depends very much on the efficiency of software your architecture. A well-architected web app can scale up RAM and CPU utilization much more closely than something modeled on zero shared state independent processes.

Additionally, even if your scaling model of RAM before CPU is the only possible one, that doesn't make the utilization effecient, and implies that higher efficiency could still be reached by scaling up RAM per machine.