* **Uvicorn**:
    * Will have the best performance, as it doesn't have much extra code apart from the server itself.

Because of this, **FastAPI** itself provides an alternative API documentation (using ReDoc), which you can access at <a href="http://127.0.0.1:8000/redoc" class="external-link" target="_blank">http://127.0.0.1:8000/redoc</a>:

Then you just do the same in your tests.

E.g.:

* To pass a *path* or *query* parameter, add it to the URL itself.
* To pass a JSON body, pass a Python object (e.g. a `dict`) to the parameter `json`.
* If you need to send *Form Data* instead of JSON, use the `data` parameter instead.

!!! check "**FastAPI** uses it to"
    Handle all the core web parts. Adding features on top.

    The class `FastAPI` itself inherits directly from the class `Starlette`.

    So, anything that you can do with Starlette, you can do it directly with **FastAPI**, as it is basically Starlette on steroids.

During the development, I also contributed to <a href="https://www.starlette.io/" class="external-link" target="_blank">**Starlette**</a>, the other key requirement.

## Development

By the time I started creating **FastAPI** itself, most of the pieces were already in place, the design was defined, the requirements and tools were ready, and the knowledge about the standards and specifications was clear and fresh.

## Future

That documentation will show up in the Swagger UI at `/docs` in your API, and it will let external developers know how to build the *external API*.

This example doesn't implement the callback itself (that could be just a line of code), only the documentation part.

!!! tip
    The actual callback is just an HTTP request.

    embed: Annotated[
        bool,
        Doc(
            """
            When `embed` is `True`, the parameter will be expected in a JSON body as a
            key instead of being the JSON body itself.

            This happens automatically when more than one `Body` parameter is declared.

            Read more about it in the

And you will have to make sure that it's a single process running those previous steps *even* if afterwards, you start **multiple processes** (multiple workers) for the application itself. If those steps were run by **multiple processes**, they would **duplicate** the work by running it on **parallel**, and if the steps were something delicate like a database migration, they could cause conflicts with each other.

    It will already be installed with **FastAPI**.

    ```Python hl_lines="1  4"
    {!> ../../../docs_src/python_types/tutorial013.py!}
    ```

Python itself doesn't do anything with this `Annotated`. And for editors and other tools, the type is still `str`.

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`

When you run `fastapi run`, it will run on production mode by default.

It will have **auto-reload disabled** by default.