alt Hacker NewsSure, best not to overcomplicate early if you don't need it.
PG is great and I work with it daily, but it's also not a problem to think about scale early and at least have a notional plan for what to and how to know when scale is becoming an issue in your system as you're designing it. Even PG is overkill and sqlite is more than enough for some of my projects.
There are a lot of specialized tools available, but you definitely don't need to put every one in your toolbox. Experience and observation help you make those edits -- and of course there's almost always room for improvement, but "good enough" definitely exists (until it doesn't anymore :D).
This is the way. Notionally building a space/path to scale into architecture early, but delaying implementation of that scaling component until actually needed.
Then a system gets most of the benefits of not accidentally making it torturous to rearchitect for scale, without paying the headcount / complexity cost until it's needed.