Deploying a **FastAPI** application is relatively easy.

## What Does Deployment Mean

To **deploy** an application means to perform the necessary steps to make it **available to the users**.

For a **web API**, it normally involves putting it in a **remote machine**, with a **server program** that provides good performance, stability, etc, so that your **users** can **access** the application efficiently and without interruptions or problems.

We create an async function `lifespan()` with `yield` like this:

```Python hl_lines="16  19"
{!../../../docs_src/events/tutorial003.py!}
```

Here we are simulating the expensive *startup* operation of loading the model by putting the (fake) model function in the dictionary with machine learning models before the `yield`. This code will be executed **before** the application **starts taking requests**, during the *startup*.

        json={
            "body": f"📝 Docs preview for commit {use_pr.head.sha} at: {settings.input_deploy_url}"
        },
    )
    if not (200 <= response.status_code <= 300):
        logging.error(f"Error posting comment: {response.text}")
        sys.exit(1)