Is the client threadsafe?

[Sconvai]

Hello,

I have recently captured a profile for my service and I see that instantiating Openai client consumes are around 16% of CPU. In order to reduce this overhead I am hoping if I can instantiate the client once at the module level and reuse it across all requests. Is this possible. If yes, are there any cons of doing so?

[kalyanamdewri]

Yes, for normal server usage I would create the OpenAI() client once per process and reuse it across requests instead of constructing a new client every time.

The main reason is that the Python SDK uses HTTP clients under the hood. The current SDK docs describe the sync and async clients as powered by httpx, and the docs also note that the client owns underlying HTTP resources that can be closed explicitly with .close() or by using a context manager. Reusing the client lets those HTTP resources and connection pools do their job; repeatedly constructing clients can add avoidable CPU and connection setup overhead.

Practical pattern:

from openai import OpenAI

client = OpenAI()

def handle_request(prompt: str):
    return client.responses.create(
        model="gpt-5.5",
        input=prompt,
    )

A few caveats:

• Treat the shared client as configuration, not request state. Do not mutate its API key, base URL, default headers, or other defaults per request.
• If one request needs different options, prefer per-call parameters or a derived client option rather than changing the global client for everyone.
• In async ASGI/FastAPI-style code, use AsyncOpenAI instead of sharing the sync client inside the event loop.
• In multi-process deployments, each worker process will normally have its own module-level client.
• Close the client during application shutdown if your framework has a shutdown hook.

Docs:

• https://developers.openai.com/api/reference/python

So the short version is: reuse a module-level client for the same API configuration; avoid per-request client construction unless each request genuinely needs a different client configuration.