!!! tip
    As FastAPI is an async framework, one request could start being processed, and before finishing, another request could be received and start processing as well, and it all could be processed in the same thread.

!!! check
    Bei der Einbindung von Routern müssen Sie sich keine Gedanken über die Performanz machen.

    Dies dauert Mikrosekunden und geschieht nur beim Start.

    Es hat also keinen Einfluss auf die Leistung. ⚡

### Einen `APIRouter` mit benutzerdefinierten `prefix`, `tags`, `responses` und `dependencies` einfügen

## Coroutines

**Coroutine** is just the very fancy term for the thing returned by an `async def` function. Python knows that it is something like a function that it can start and that it will end at some point, but that it might be paused ⏸ internally too, whenever there is an `await` inside of it.

The command `fastapi dev` reads your `main.py` file, detects the **FastAPI** app in it, and starts a server using <a href="https://www.uvicorn.org" class="external-link" target="_blank">Uvicorn</a>.

By default, `fastapi dev` will start with auto-reload enabled for local development.

You can read more about it in the <a href="https://fastapi.tiangolo.com/fastapi-cli/" target="_blank">FastAPI CLI docs</a>.

</details>

### Check it

For example, in Visual Studio Code, you can:

* Go to the "Debug" panel.
* "Add configuration...".
* Select "Python"
* Run the debugger with the option "`Python: Current File (Integrated Terminal)`".

It will then start the server with your **FastAPI** code, stop at your breakpoints, etc.

Here's how it might look:

<img src="/img/tutorial/debugging/image01.png">

---

If you use Pycharm, you can:

But Gunicorn supports working as a **process manager** and allowing users to tell it which specific **worker process class** to use. Then Gunicorn would start one or more **worker processes** using that class.

And **Uvicorn** has a **Gunicorn-compatible worker class**.

<div class="termy">

```console
$ python ./scripts/docs.py live

<span style="color: green;">[INFO]</span> Serving on http://127.0.0.1:8008
<span style="color: green;">[INFO]</span> Start watching changes
<span style="color: green;">[INFO]</span> Start detecting changes
```

</div>

Он запустит сайт документации по адресу: `http://127.0.0.1:8008`.

Es unterstützt auch die Ausführung von <a href="https://github.com/tiangolo/uvicorn-gunicorn-fastapi-docker#pre_start_path" class="external-link" target="_blank">**Vorab-Schritten vor dem Start** </a> mit einem Skript.

!!! tip "Tipp"

A container is running as long as the **main process** (command or program) is running.

A container normally has a **single process**, but it's also possible to start subprocesses from the main process, and that way you will have **multiple processes** in the same container.

## Use Case

Let's start with an example **use case** and then see how to solve it with this.

Let's imagine that you have some **machine learning models** that you want to use to handle requests. 🤖