I don't think the "Make it Right" part should or can reasonably be left out of the equation, otherwise I could just compute something if all you care about is s

I don't think the "Make it Right" part should or can reasonably be left out of the equation, otherwise I could just compute something if all you care about is speed. That said, I have used a performance-first approach several times using own old and new solutions and libraries and have found early benchmarks to be a great tool to weed out untenable (i.e. order-of-magnitude slower) stuff. This then can mean I have to write fewer tests to make plausible my own or a 3rd party solution does in fact what I expect it to do. At a certain point performance becomes correctness.