async_fastapi_cache.py

import asyncio
from functools import wraps

from fastapi import FastAPI, Request
from fastapi.responses import HTMLResponse
from fastapi.templating import Jinja2Templates


def cache_response(func):
    """
    Decorator that caches the response of a FastAPI async function.

    Example:
    ```
        app = FastAPI()

        @app.get("/")
        @cache_response
        async def example():
            return {"message": "Hello World"}
    ```
    """
    response = None

    @wraps(func)
    async def wrapper(*args, **kwargs):
        nonlocal response
        if not response:
            response = await func(*args, **kwargs)
        return response

    return wrapper


app = FastAPI()
templates = Jinja2Templates(directory="templates")


@app.get("/", response_class=HTMLResponse)
@cache_response
async def home_page(request: Request):
    await asyncio.sleep(2)
    return templates.TemplateResponse("hello_world.html", context={"request": request})


@app.get("/json/")
@cache_response
async def json_example():
    await asyncio.sleep(2)
    return {"message": "Hello World"}

Companion blog post here: https://blog.osull.com/2022/06/03/a-very-simple-async-response-cache-for-fastapi/