Fastapi with Aiohttp not providing expected results

I am new to asynchronous programming in python. Below are two scripts(which perform the same operation) one in Fastapi + aiohttp while other is basic Flask + requests library:

## Flask

def fetch1(url):
    x = requests.get(url)                 # First hit to the url 
    data = x.json()                       # Grab response
    return fetch2(data['uuid'])           # Pass uuid to the second function for post request

def fetch2(id):
    url2 = "http://httpbin.org/post"
    params = {'id': id}
    x = requests.post(url2, json=params)
    return x.json() 

@app.route('/')
def main():
    url = 'http://httpbin.org/uuid'
    data = fetch1(url)    
    return {"message":"done"}

and the fastapi couterpart:

async def fetch1(session, url):
    async with session.get(url) as resp:                
        data = await resp.json()                       
        return await fetch2(session, data['uuid'])     

async def fetch2(session, id):
    url2 = "http://httpbin.org/post"
    params = {'id': id}
    async with session.post(url2, json=params) as resp:
        return await resp.json()


@app.get("/")
async def main():
    url = 'http://httpbin.org/uuid'
    async with aiohttp.ClientSession() as session:
        data = await fetch1(session, url)
        return {"message":"done"}

As a sample benchmark testing (Using Apache Bench), I had fired 500 requests at 100 concurrency, while Flask took 7 seconds(approx) to complete the operation fastapi takes 4.5 to do the same(which is not that great).Is my async code blocking in nature or Am I missing something.Any help will be appreciated.