The majority of companies are building their stuff entirely in the cloud, where network speed scales with the instance size. I have had to explain this to multiple engineers at multiple companies, who are surprised to learn that network bandwidth isn’t unlimited.

As to your database comment, IME most of the time the bottleneck is the ORM and/or language. The amount of work an ORM does to generate a representation of a row is frankly shocking. Not understanding the cost of context-switching is the language half of it: Python, of course, is single-threaded, but you can use greenlets to cheat, because they’re I/O bound — except for all of them serializing behind a single process handling serdes for the queries.