That is sensible advice, but sometimes you cannot slowly iterate and getting to your performance target from a simple prototype realistically requires a step ch

That is sensible advice, but sometimes you cannot slowly iterate and getting to your performance target from a simple prototype realistically requires a step change in your architecture. Often you know enough of your problem that you can determine analytically that certain approaches will never deliver sufficient performance. In that case you might want a performance prototype after you created a functional prototype, then iterate by adding functionality while checking for performance regressions.