alt Hacker News> I suspect we will eventually end up in a place where the vast majority of applications are happy on a single box, and only twitter scale things need to care about this stuff.
We're already there IMO. A single box can scale up so much more than people expect these days - over a thousand cores and terabytes of RAM. The people coming up with overcomplicated architectures and mandatory high availability get in the way of it.
A single box may have that much resources available, but no software will use them efficiently alone. You end up having issues with NUMA, with your pagetable growing significantly forcing you to deal with hugepages and eventually memory fragmentation, and who knows what other kind of lovecraftian horror coming from the sheer complexity of a single system with that much resources. Turns out scaling vertically also has cost. That's why eventually you still want to scale horizontally. And that's not overcomplicating things for the fun of it, it's just tradeoffs.