Yes, my point is it will hold, but it won't hold 50M users, and if you take off you'll be scrambling to rewrite it from scratch. So a flexible architecture that

Yes, my point is it will hold, but it won't hold 50M users, and if you take off you'll be scrambling to rewrite it from scratch. So a flexible architecture that is simple but can scale (as an architecture) might be a better choice than the simplest possible design you can make.