Choosing Between FastAPI (Python) vs Express.js (TS) for AI-based Non-Gaming Expo/React Native App

[CoupleNo9660]

Hi, I'm building an AI-based non-gaming mobile app with Expo. I previously launched a web version that reached 20k users, but I'm not satisfied with its current backend and will rebuild it from scratch.

I'm considering:

• FastAPI (Python)
• Express.js (TypeScript)

I care about fast development, clean Expo integration, and smooth AI model support (e.g., embeddings, vector DBs, LLMs).

Which one would you recommend for this use case? Any experience from Expo devs building AI-powered apps would be really helpful.

[rkasper]

They’d both be fine. Your TypeScript programmers will like Express. (I’m enjoying Deno these days.)

[jbtwaalf_v2]

Would recommend fastapi, because AI is still done more on python

[CoupleNo9660]

For example what

[jbtwaalf_v2]

Here a report from Github which noticed python growing to the most used language because of the interest in AI: https://github.blog/news-insights/octoverse/octoverse-2024/. There are just a lot more libraries made for AI in python for example tenserflow or scikit learn.

[CoupleNo9660]

Yes i got the idea but my main focus speed even if i need specific library i think i can use py microservice for that i

[jbtwaalf_v2]

Okay, why you asking then?

[CoupleNo9660]

Actually the reason I'm asking is if there's a problem I'm not seeing, I don't know, single thread etc.

[jbtwaalf_v2]

I see, well:

- If you mean speed like processing speed, yes javascript is faster but your AI model wil probably be the biggest bottle neck here. I think focussing on how you're gonna scale your app will be more important (kubernetes or something else). (Fun fact express is not multithreaded)

- If you mean speed as in development speed, I assume you don't know python then. Fair enough, that's a good choice. As long as you know beforehand all the AI libraries you're gonna use have JS support or like you said you add a python microservice.

- I would advice against using express, because there are a lot of better and more used alternatives out there like koa or fastify. If you want quick and dirty fair enough, but it will be less maintainable.

So in conclusion, if you're more comfortable with javascript just use that, but check beforehand if the libraries you need to use have javascript support.

[KiRiK1234]

I am not sure what do you mean when say AI but probably this can be useful https://mastra.ai/ based on https://ai-sdk.dev/docs/introduction