[necovek]

That's not what was said. Python application code is the bottleneck. As evident from the benchmarks for FastWSGI, even Flask the framework is a bottleneck: pure Python vs Flask went from 70k RPS to 9k RPS.

Python does have a huge performance penalty for basic computation, which is why it has a bunch of C-based libraries that provide bulk-operations that avoid it. If properly used (you rarely need to roll your own with a number of compiled libraries present), Python itself is not a bottleneck. One can argue if that's still Python, but at the very least, it's idiomatic Python development: I hope you don't use Python to prove that pure dynamic languages can outperform compiled languages, but to develop and deliver applications faster using Python's expressiveness.

People bring up GIL as well: it will affect your application startup time and memory usage since you can trivially avoid it by running multiple Python processes. But performance of executing code itself will only be minimally affected if you switch to multi-processing (of course, if memory pressure is so high that all those Python libraries loaded multiple times in memory is affecting your app, that can hinder performance, but that's going to be pretty rare).