[Rapzid]

I'm biased as I usually come on to the scene because a company has a successful product and is experiencing engineering scaling pains.

That said, in my experience, CPU is often the ultimate bottleneck with PHP, Ruby, Python, and.. Like everything. Over the years serializers have often been a pain point; XML in PHP and RoR, and the Rails "serializers" currently. Any sort of mapping or hydration(which is a LOT of what happens in web apps) is comparatively slow, often order of magnitude or more, over something like nodejs, C#, golang, and etc.

> Most bottlenecks are either that database choices or poor code/design choices by developers

Perhaps in sheer quantity, but with experience those are often low hanging fruit. After those are addressed you are left with the pain of the language and framework inefficiencies.