By nontrivial I mean 'application which, in your document database, requires multi-document updates to perform some individual logical operations'. This is a r

By nontrivial I mean 'application which, in your document database, requires multi-document updates to perform some individual logical operations'. This is a rather low bar :-). The fact is, the vast majority of projects that programmers are working on are less computationally complex than stack overflow. That's not to say that forum software is all that complex, more that most problems are pretty simple. Of course there are real reasons to use scale out - I simply advocate thinking hard about whether your problem will ever truly need it before taking the substantial complexity hit of coding for it.