> Honestly, if you're bottlenecking on singleton access, that's design smell worth addressing, not the guard variable.

There's a large group of engineers who are totally unaware of Amdahl's law and they are consequently obsessed with the performance implications of what are usually most non-important parts of the codebase.

I learned that being in the opposite group of people became (or maybe has been always) somewhat unpopular because it breaks many of the myths that we have been taught for years, and on top of which many people have built their careers. This article may or may not be an example of that. I am not reading too much into it but profiling and identifying the actual bottlenecks seems like a scarce skill nowadays.