This idea of **asynchronous** code described above is also sometimes called **"concurrency"**. It is different from **"parallelism"**.

**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

### Concurrent Burgers

In this section you will see how to manage authentication and authorization with the same OAuth2 with scopes in your **FastAPI** application.

!!! warning
    This is a more or less advanced section. If you are just starting, you can skip it.

    You don't necessarily need OAuth2 scopes, and you can handle authentication and authorization however you want.

  }

  /**
   * Returns the name of the query parameter at `index`. For example this returns `"a"`
   * for `queryParameterName(0)` on `http://host/?a=apple&b=banana`. This throws if
   * `index` is not less than the [query size][querySize].
   *
   * | URL                               | `queryParameterName(0)` | `queryParameterName(1)` |
   * | :-------------------------------- | :---------------------- | :---------------------- |

- [`KTIJ-25448`](https://youtrack.jetbrains.com/issue/KTIJ-25448) When project JDK is less than one defines in jvmToolchain block, run with Idea fails with `has been compiled by a more recent version of the Java Runtime`

under the `kubelet` process. On systems with `journalctl` the following is an example command line
to view the last 1000 `kubelet` logs via the `less` utility to allow for `vi`-style searching:

```console
$ journalctl -t kubelet -n 1000 | less
```

#### GKE via Stackdriver Log Viewer

Each GKE cluster's will have many categories of logs collected by Stackdriver.  Logs can be monitored via

     * gaps. For example, an insecure TLS connection is capable of negotiating HTTP/2 with ALPN and
     * it also has a regular-looking handshake.
     *
     * **This feature is not supported on Android API levels less than 24.** Prior releases lacked
     * a mechanism to trust some hosts and not others.
     *
     * @param hostname the exact hostname from the URL for insecure connections.
     */

            AND LOWER THAN CURRENT BASE VERSION (from `version.txt` on this branch).
            The difference must identically match <a href="${apiChangesJsonFile.asFile.path}">accepted-public-api-changes.json</a>, no more, no less - otherwise the task will fail.
            </p>
            ${writeFilterPreset(project)}
""".stripIndent()

        it.renderer.set(EnrichedReportRenderer.class)
    } as Action)

Dann könnten Sie dieses Python-Programm aufrufen:

<div class="termy">

```console
// Hier legen wir die Umgebungsvariable noch nicht fest
$ python main.py

// Da wir die Umgebungsvariable nicht festgelegt haben, erhalten wir den Standardwert

Hello World from Python

// Aber wenn wir zuerst eine Umgebungsvariable erstellen

When you run `fastapi dev`, it will run on development mode.

By default, it will have **auto-reload** enabled, so it will automatically reload the server when you make changes to your code. This is resource intensive and could be less stable than without it, you should only use it for development.

By default it will listen on the IP address `127.0.0.1`, which is the IP for your machine to communicate with itself alone (`localhost`).

## `fastapi run`

!!! note
    When defining a <a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a>, include the most specific type first, followed by the less specific type. In the example below, the more specific `PlaneItem` comes before `CarItem` in `Union[PlaneItem, CarItem]`.

=== "Python 3.10+"

    ```Python hl_lines="1  14-15  18-20  33"