[inhumantsar]

That's the point though. If you want to focus your engineering time on optimization and code quality, then of course you can scale to SO's size with 9 servers and a simple architecture.

If you're still growing and more interested in delivering tons of features quickly, and/or don't have the ability to attract world leading talent, then a more complicated architecture with clear boundaries is often a better call than delivering relatively few features with obsessive rigor in a monolithic codebase.

[Yeroc]

You'll only need the expertise to perform in-depth optimization if you're scaling to the level of Stack Overflow though. For the vast majority of sites it won't be a concern. The simpler architecture should be the default because local method calls are easily 2 orders of magnitude faster than a network roundtrip (yes I know that's not the whole story). I'm not sure how or why creating clear boundaries without the RPC crutch suddenly became insurmountable.