They both have their place. Ideally the design doc flows out from the proof of concept to document the non-trivial assumptions and decisions. But nothing beats

They both have their place. Ideally the design doc flows out from the proof of concept to document the non-trivial assumptions and decisions. But nothing beats an actual PoC to demonstrate that something will actually work. I like the phrase “weaponize” to refer to the evolution of a PoC into a workable application.