> I don't think it's true that most applications just run a single db-and-application node. I've never worked on such an application. Rather than applications

> I don't think it's true that most applications just run a single db-and-application node. I've never worked on such an application. Rather than applications you've worked on (many of us spend years on end working on a narrow range of applications), consider software you use (most of us flip between multiple applications every day spanning the gamut of uses). Ignore, for a moment, whatever you know about their implementation, and focus on the user-facing functionality. Do even half of them logically communication between application nodes? (Consider that there is still a rich class of software that is fully capable of running locally on the "client"'s computer!)