Scalability is like an abstract painting. It's unique to one's infrastructure. Its writing or sometimes postmortem makes good brain fertilizer. Not so much more. Beyond that I wouldn't rush to implement scalability du jour.

A setup that works for a certain service won't necessarily work for another unless yours is a very close replica. Based on my experience in this area, and I'm a performance seeking nut, each platform, and even each traffic pattern, needs its own thinking hat.

That's what makes it so fun!