This one also looks pretty obvious "in foresight" (using the same tools that existed back then. Maybe owner dedupe might be less obvious and require a bit of knowledge and probing into actual data, but for rw vs ro you are fine knowing nothing?) and you forgot the napkin math re. how much your precious "time to market" would have been delayed by.

It's also not nothing, otherwise it would never be optimized away now, but left as is. After all, wasting time on optimization delays "time to market" for other useful features.

I also don't get the reference to YouTube, it's a very successful product, how was it butchered by good system design???