In what cases will there be no difference between synchronous code and asynchronous?

Question

Python

I have a small tornado project that completes a fully synchronous request in 300-400 milliseconds. There is both work with the database and calls to third-party APIs. I spent some time, rewrote everything in an asynchronous style: all requests to third-party APIs and services, switched to an asynchronous engine for the database and wrote my own small ORM for it too, refactored some parts of the code, added caching - but, for some reason, request time remains the same. That is exactly the same 300-400 milliseconds. That is, it has not decreased at all. I'm testing on a local server using Insomnia.
So what could be my mistake? What could I be missing?

Answer 1

Can Insomnia do load testing?
Create a load with parallel queries (at least with ab) and compare.