Cloudflare Python Workers: Fast Cold Starts, Packages, and a uv-First Workflow

Cloudflare has announced significant improvements to its Python Workers platform, enabling developers to create fast and scalable serverless applications. The key updates include:

• Fast cold starts: Cloudflare Workers now achieve exceptionally fast cold starts, thanks to dedicated memory snapshots, which result in a 2.4x faster start time compared to AWS Lambda without SnapStart and 3x faster than Google Cloud Run.
• Package support: Python Workers now support any package supported by Pyodide, the WebAssembly runtime powering Python Workers, including pure Python packages and many packages that rely on dynamic libraries.
• uv-first workflow: Cloudflare has built tooling around uv to make package installation easy and efficient.

Developers can leverage these improvements to create scalable and fast serverless applications using Python. With Cloudflare Workers, developers can deploy Python applications globally in under 2 minutes, without worrying about infrastructure or scaling. The free tier offers 100,000 requests per day and 10ms CPU time per invocation.

Practical Implications for Developers

• Write Python applications that can be deployed globally in under 2 minutes using Cloudflare Workers.
• Take advantage of fast cold starts and scalable infrastructure to create high-performance serverless applications.
• Use Python Workers to create a wide range of applications, including rendering HTML templates, modifying server responses, building chat rooms, and more.

Example Use Case

Deploy a FastAPI app across the world with fast cold starts in less than two minutes using the following code:

from fastapi import FastAPI
from workers import WorkerEntrypoint
import asgi

app = FastAPI()
@app.get("/")
async def root():
    return {"message": "This is FastAPI on Workers"}

class Default(WorkerEntrypoint):
    async def fetch(self, request):
        return await asgi.fetch(app, request.js_object, self.env)

# Deploy the application using pywrangler
$ uv tool install workers-py
$ pywrangler init --template https://github.com/cloudflare/python-workers-examples/03-fastapi
$ pywrangler deploy

This code demonstrates how to create a FastAPI application and deploy it using Cloudflare Workers, taking advantage of fast cold starts and scalable infrastructure.