Scaling out vs. scaling up is the false dilemma, the answer is both at the same time solving the bottlenecks you have using the time and resources you have. The "vast majority" of applications do not map well to an n-wide map-reduce-esque design, the "vast majority" of applications bottleneck on an authoritative datastore's I/O capacity.
I'm the sysadmin (not the dba) for a website that does 30K http req/s at the edge, and our mysql cluster does about 3000 req/s during mid-day with most queries in the 1 - 5ms range.
Highscalability is a terrible place to get started, its a great place to share notes but if you get started there you will waste insane amounts of time on architecture astronaut nonsense.
I'm the sysadmin (not the dba) for a website that does 30K http req/s at the edge, and our mysql cluster does about 3000 req/s during mid-day with most queries in the 1 - 5ms range.
Highscalability is a terrible place to get started, its a great place to share notes but if you get started there you will waste insane amounts of time on architecture astronaut nonsense.