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Anyway, in any of the cases above, FastAPI will still work asynchronously and be extremely fast.

But by following the steps above, it will be able to do some performance optimizations.

## Technical Details

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# Features

## FastAPI features

**FastAPI** gives you the following:

### Based on open standards

OpenAPI has a way to define multiple security "schemes".

By using them, you can take advantage of all these standard-based tools, including these interactive documentation systems.

OpenAPI defines the following security schemes:

* `apiKey`: an application specific key that can come from:
    * A query parameter.
    * A header.
    * A cookie.
* `http`: standard HTTP authentication systems, including:

The following arguments are supported:

* `allow_origins` - A list of origins that should be permitted to make cross-origin requests. E.g. `['https://example.org', 'https://www.example.org']`. You can use `['*']` to allow any origin.

* Update `scripts/test-cov-html.sh` to allow passing extra parameters like `-vv`, for development.

## 0.11.0

### `Response`

The main `Response` class, all the other responses inherit from it.

You can return it directly.

It accepts the following parameters:

* `content` - A `str` or `bytes`.
* `status_code` - An `int` HTTP status code.
* `headers` - A `dict` of strings.
* `media_type` - A `str` giving the media type. E.g. `"text/html"`.

* not use `Annotated`

...Python has a little special syntax for that.

Pass `*`, as the first parameter of the function.

Python won't do anything with that `*`, but it will know that all the following parameters should be called as keyword arguments (key-value pairs), also known as <abbr title="From: K-ey W-ord Arg-uments"><code>kwargs</code></abbr>. Even if they don't have a default value.

```Python hl_lines="7"

    ```

**FastAPI** provides a shortcut for these cases, in where the dependency is *specifically* a class that **FastAPI** will "call" to create an instance of the class itself.

For those specific cases, you can do the following:

Instead of writing:

=== "Python 3.8+"

    ```Python
    commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
    ```

=== "Python 3.8+ non-Annotated"

    !!! tip

    {!> ../../../docs_src/query_params_str_validations/tutorial004.py!}
    ```

This specific regular expression pattern checks that the received parameter value:

* `^`: starts with the following characters, doesn't have characters before.
* `fixedquery`: has the exact value `fixedquery`.
* `$`: ends there, doesn't have any more characters after `fixedquery`.