Does FastAPI Work With Netlify?
FastAPI can run on Netlify Functions, but you'll need to adapt your application structure since Netlify's serverless environment has specific constraints.
Quick Facts
How FastAPI Works With Netlify
FastAPI is a traditional ASGI framework designed to run as a long-lived server, while Netlify Functions are stateless, short-lived serverless compute units. To use them together, you must wrap your FastAPI app or individual route handlers as serverless functions. This typically means deploying FastAPI endpoints as separate Netlify Functions rather than a monolithic application. You can either use adapters like Mangum (an ASGI-to-Lambda adapter) to wrap your entire FastAPI app, or refactor routes into individual functions. The developer experience involves writing your FastAPI logic but then strategically breaking it into function-sized chunks that fit Netlify's execution model. Cold starts can impact performance, and you lose some benefits of FastAPI's built-in dependency injection across routes when splitting into functions. Alternatively, you could deploy the full FastAPI application to a traditional host (like Render or Railway) and use Netlify only for static assets and edge functions, which is often the more practical approach for complex APIs.
Best Use Cases
FastAPI with Mangum on Netlify Functions
pip install fastapi mangumfrom fastapi import FastAPI
from mangum import Mangum
app = FastAPI()
@app.get("/api/hello")
async def hello(name: str = "World"):
return {"message": f"Hello, {name}!"}
@app.get("/api/items/{item_id}")
async def get_item(item_id: int):
return {"item_id": item_id, "name": "Sample Item"}
# Export handler for Netlify Functions
handler = Mangum(app)
# In netlify.toml:
# [[functions]]
# node_bundler = "esbuild"
# directory = "functions"
# python_version = "3.11"Known Issues & Gotchas
Cold start latency: Netlify Functions have startup overhead, making FastAPI's typical sub-10ms response times much slower on first invocation
Fix: Use Netlify's scheduled functions for warming, or deploy FastAPI to a traditional always-on server if latency is critical
Request/response size limits: Netlify Functions have payload size caps (6MB), problematic for large file uploads or responses
Fix: Use presigned URLs for file uploads/downloads, or stream through separate CDN/blob storage
No persistent connections: WebSockets and long-polling won't work in serverless; FastAPI's async features become less valuable
Fix: Redesign real-time features using event-based architecture (webhooks, message queues) or deploy FastAPI separately
Environment variable management: FastAPI's config patterns don't align well with Netlify's function environment setup
Fix: Use netlify.toml for environment variables and adjust FastAPI settings module accordingly
Alternatives
- •Next.js API Routes + Netlify (native TypeScript, better DX for full-stack)
- •Express.js + Netlify Functions + Serverless Framework (simpler Node.js alternative)
- •FastAPI + Railway/Render (dedicated Python hosting, no serverless compromises)
Resources
Related Compatibility Guides
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