r/AskComputerScience • u/Ok-Cut-6424 • 4d ago

Node.js (Socket.io + Prisma) vs. FastAPI (SQLAlchemy) for an isolated Chat microservice?

Hey folks,

Building an isolated chat microservice consumed by other services in our ecosystem. Auth/users are handled externally by a dedicated Identity service, so our service only handles private topics/rooms, participant access, message history, and an embeddable <iframe> widget.

Stuck choosing between two stacks:

  1. Node.js + Prisma + Socket.io

    • Pros: Native room management (socket.join, io.to().emit), simple single-language codebase for both backend and the iframe widget.

    • Cons: Generating interactive API docs for other teams isn't as seamless out of the box.

  2. Python + FastAPI + SQLAlchemy

    • Pros: Automatic OpenAPI/Swagger docs (/docs) out of the box makes sharing API contracts effortless.

    • Cons: Bare-bones WebSockets mean building a custom ConnectionManager for rooms/disconnects, plus writing JS for the iframe anyway.

Is rolling custom WebSocket room logic in FastAPI a pain compared to Socket.io's battle-tested rooms, or is FastAPI’s clean OpenAPI generation worth the plumbing?

Would love to hear how you'd approach this!

2 Upvotes

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3

u/telmo_trooper 3d ago

I don't think generating API documentation should be a major concern for any stack, there's good support for that in almost every language. LLMs are also very competent at automating that aspect of the work.

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u/Ok-Cut-6424 3d ago

Oh ok I see in this case the first option makes more sens.

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u/T_Thriller_T 3d ago

I'd personally probably make the decision based on familiarity and comfort more than other stuff. If you have someone who is good with python? Great!

If your whole team is more knowledgeable in JavaScript, go there.

What could be helpful is that custom room logic may be more modular in the future. But that is really a big could.

Additionally, I am a little confused you listed sqlalchemy yet no database equivalent on the JavaScript side.

What do you intend Sqlalchemy to be used for?

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u/Ok-Cut-6424 3d ago

I am comfortable with both as I have already done kinda big projects in both stacks now as you said it will depend on my team familiarity with either.

what do you mean by modular please?

In both case PostgreSQL is the default db choice, I mentioned Prisma and SqlAlchemy for ORM and db migrations