# Создание клиента на каждый запрос
@app.get("/orders/{id}")
async def get_order(id: int):
    async with httpx.AsyncClient(timeout=30.0) as client:
        r = await client.get(f"http://orders/{id}")
    return r.json()

# Один клиент на жизнь приложения
from contextlib import asynccontextmanager

@asynccontextmanager
async def lifespan(app: FastAPI):
    app.state.http = httpx.AsyncClient(
        base_url="http://orders",
        timeout=httpx.Timeout(5.0, read=30.0),
        limits=httpx.Limits(max_connections=100, max_keepalive_connections=20),
    )
    yield
    await app.state.http.aclose()

app = FastAPI(lifespan=lifespan)

def get_http(request: Request) -> httpx.AsyncClient:
    return request.app.state.http

@app.get("/orders/{id}")
async def get_order(id: int, http: httpx.AsyncClient = Depends(get_http)):
    r = await http.get(f"/{id}")
    return r.json()