Exactly THIS!

I found an excellent way to avoid premature abstraction and optimization and to write better software in general was to explicitly consider v1.x a throw-away.

Build something expedient that works well enough to deploy in the field, get actual user feedback and system metrics (e.g., where are the actual bottlenecks). Do a few iterations on user feedback and system metrics. NOW, you are much further down the road to a true final spec, and you can use that real information to design the real system to scale up on.

One Test Is Worth A Thousand Opinions.

This plan first tests your ideas against the real world of users, hardware, and data flows, and keeps a lot of technical debt out of the scaling system.

I discovered it a bit by accident, having previously been really big on early abstraction and planning, but sort of having to do this in one startup, and it was a real eye-opener how well it worked.

So you rediscovered "build one to throw away", popularized in The mythical man-month, afaik?