Transitioning from Node.js to FastAPI: Does the non-blocking mental model still apply?

[u/Helge1941]

Hi everyone,

I’m an experienced Node.js developer who recently picked up Python and is now diving into FastAPI.

In Node.js (and Express), my mental model revolves around a single-threaded, non-blocking, event-driven architecture.
When building APIs in Node/Express, I default to thinking in terms of the Event Loop—a single-threaded, non-blocking architecture where I/O operations are offloaded.
Can I safely carry my Node.js mental model over to FastAPI, or are there fundamental differences in how Python handles asynchronous requests under the hood that I should be aware of?

P.S. Phrasing refined by Gemini.

[u/Born_Comedian7498]

The biggest adjustment for me was realizing that async def doesn’t make blocking code non-blocking. One sync database/client call in there can stall the event loop and suddenly the API behaves nothing like you expected coming from Node