* If you are comparing Uvicorn, compare it against Daphne, Hypercorn, uWSGI, etc. Application servers.
* **Starlette**:
    * Will have the next best performance, after Uvicorn. In fact, Starlette uses Uvicorn to run. So, it probably can only get "slower" than Uvicorn by having to execute more code.

I'll show you some concrete examples in the next chapters.

---

Then the next concepts to consider are all about the program running your actual API (e.g. Uvicorn).

## Program and Process

# Run a Server Manually

## Use the `fastapi run` Command

In short, use `fastapi run` to serve your FastAPI application:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> run <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

But I'll show you how to improve that next. 🤓

## Custom Operation IDs and Better Method Names

You can **modify** the way these operation IDs are **generated** to make them simpler and have **simpler method names** in the clients.

This decoupling of parts, and being a "microframework" that could be extended to cover exactly what is needed was a key feature that I wanted to keep.

Given the simplicity of Flask, it seemed like a good match for building APIs. The next thing to find was a "Django REST Framework" for Flask.

!!! check "Inspired **FastAPI** to"
    Be a micro-framework. Making it easy to mix and match the tools and parts needed.

The only new thing is the `callbacks=invoices_callback_router.routes` as an argument to the *path operation decorator*. We'll see what that is next.

## Documenting the callback

The actual callback code will depend heavily on your own API app.

And it will probably vary a lot from one app to the next.

It could be just one or two lines of code, like:

```Python
callback_url = "https://example.com/api/v1/invoices/events/"

But it's signed. So, when you receive a token that you emitted, you can verify that you actually emitted it.

That way, you can create a token with an expiration of, let's say, 1 week. And then when the user comes back the next day with the token, you know that user is still logged in to your system.

```Python hl_lines="3" title="app/routers/items.py"
{!../../../docs_src/bigger_applications/app/routers/items.py!}
```

#### How relative imports work

!!! tip
    If you know perfectly how imports work, continue to the next section below.

A single dot `.`, like in:

```Python
from .dependencies import get_token_header
```

would mean:

But even if you never use **FastAPI**, you would benefit from learning a bit about them.

!!! note
    If you are a Python expert, and you already know everything about type hints, skip to the next chapter.

## Motivation

Let's start with a simple example:

```Python
{!../../../docs_src/python_types/tutorial001.py!}
```

Calling this program outputs:

```
John Doe
```

    assert response.headers["content-type"] == "text/html; charset=utf-8"
    assert "window.opener.swaggerUIRedirectOauth2" in response.text


def test_redoc():
    response = client.get("/redoc")
    assert response.status_code == 200, response.text
    assert response.headers["content-type"] == "text/html; charset=utf-8"
    assert "redoc@next" in response.text