I completely disagree. If the program doesn't have "hotspots" then it's probably pretty fast and it's following Knuth's advice. But in my experience most applic

I completely disagree. If the program doesn't have "hotspots" then it's probably pretty fast and it's following Knuth's advice. But in my experience most applications are completely littered with "hotspots" - endpoints taking 5+ seconds to respond, reports taking minutes or hours to generate, stuff like that. I've never worked on an application where I didn't quickly find multiple easily avoidable hotspots. The average developer, at least in my area of the world, just really doesn't understand how to write performant code at all. They write algorithms with terrible time and/or space complexity, they write inefficient database queries, design their database schemas in ways that don't even allow efficient queries etc. Then they add caching to compensate for their crappy system design and stuff like that, bloating the system with lots of unnecessary code. They store the data naively then spend significant processing time preparing the data for delivery rather than just storing the data in an ideal format in the first place. Lots of stuff like that.