Abnormal Benchmark: FastAPI+Uvicorn Outperforms Granian Drastically – Seeking Help

[langkai1]

Help Needed: Abnormal Performance - Granian 6x Slower Than Uvicorn in FastAPI Benchmark

I'm running wrk benchmark tests on a minimal FastAPI application with two ASGI servers: Uvicorn and Granian.

The results are completely abnormal and counterintuitive:

• Uvicorn: ~7500 Requests/sec
• Granian: ~1100 Requests/sec

Granian is supposed to be a high-performance Rust-based ASGI server, but in my test, it is 6x slower than Uvicorn.

I need help identifying what is wrong with my setup, commands, or environment.

---

Test Environment

• Python: 3.14.3
• OS: WSL2 — Ubuntu 24.04
• Dependencies:

dependencies = [
    "fastapi[standard]>=0.135.2",
    "granian>=2.7.2",
    "httptools>=0.7.1",
    "uvicorn>=0.42.0",
]

Application Code (test_fastapi.py)

-Minimal test app with no extra logic:

# -*- coding: utf-8 -*-
from fastapi import FastAPI
from pydantic import BaseModel
app = FastAPI()

class Health(BaseModel):
    status: str

@app.get(
    "/health",
    response_model=Health,
)
def read_root():
    return Health(
        status="ok"
    )

Startup Commands

-Uvicorn (High Performance)

uv run uvicorn test_fastapi:app --host 127.0.0.1 --port 8080 --workers 2 --log-level critical --loop uvloop --http httptools

-Granian (Very Slow)

uv run granian test_fastapi:app --host 127.0.0.1 --port 8080 --workers 2  --loop uvloop --interface asgi

-Benchmark Command (wrk)

wrk -t4 -c100 -d10s -H "Content-Type: application/json" http://localhost:8080/health

Actual Results

FastAPI + Uvicorn: Requests/sec: 7537
FastAPI + Granian: Requests/sec: 1159.40
What I’ve Tried
Enabled for both servers uvloop
Set same worker count: 2
Disabled logging for Uvicorn
Used ASGI interface for Granian

Questions & Help Needed

1. Are my Granian startup parameters missing critical performance flags?
2. Is Python 3.14.3 incompatible with Granian?
3. Is there a configuration issue causing the huge performance drop?
4. What settings should I change to make Granian perform normally?
5. If you have any suggestions, please help!

[gi0baro]

Switch your read_root function to be async.

FastAPI does a bunch of stuff with threadpool executors to serve sync methods. That plays poorly with Granian. FYI the same plays with uvicorn, if you switch to async methods RPS increase on uvicorn as well.