At some point, Swagger was given to the Linux Foundation, to be renamed OpenAPI.

That's why when talking about version 2.0 it's common to say "Swagger", and for version 3+ "OpenAPI".

!!! check "Inspired **FastAPI** to"
    Adopt and use an open standard for API specifications, instead of a custom schema.

<img class="shadow" src="/img/deployment/concepts/image01.png">

---

Now that we know the difference between the terms **process** and **program**, let's continue talking about deployments.

## Running on Startup

### Create the `FastAPI` app

```Python hl_lines="46"
{!../../../docs_src/nosql_databases/tutorial001.py!}
```

### Create the *path operation function*

## Motivation

Let's start with a simple example:

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

Calling this program outputs:

```
John Doe
```

The function does the following:

* Takes a `first_name` and `last_name`.
* Converts the first letter of each one to upper case with `title()`.

    * PR [#294](https://github.com/tiangolo/fastapi/pull/294).

## 0.28.0

* Implement dependency cache per request.
    * This avoids calling each dependency multiple times for the same request.
    * This is useful while calling external services, performing costly computation, etc.

    But **FastAPI** will know that it has to solve `query_extractor` first, to pass the results of that to `query_or_cookie_extractor` while calling it.

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

    ```Python hl_lines="5  22"
    {!> ../../../docs_src/encoder/tutorial001.py!}
    ```

In this example, it would convert the Pydantic model to a `dict`, and the `datetime` to a `str`.

The result of calling it is something that can be encoded with the Python standard <a href="https://docs.python.org/3/library/json.html#json.dumps" class="external-link" target="_blank">`json.dumps()`</a>.

!!! tip
    You'll see what other "things", apart from functions, can be used as dependencies in the next chapter.

Whenever a new request arrives, **FastAPI** will take care of:

* Calling your dependency ("dependable") function with the correct parameters.
* Get the result from your function.
* Assign that result to the parameter in your *path operation function*.

```mermaid
graph TB

  - author: Nils de Bruin
    author_link: https://medium.com/@nilsdebruin
    link: https://medium.com/data-rebels/fastapi-authentication-revisited-enabling-api-key-authentication-122dc5975680
    title: 'FastAPI authentication revisited: Enabling API key authentication'
  - author: Nick Cortale
    author_link: https://nickc1.github.io/
    link: https://nickc1.github.io/api,/scikit-learn/2019/01/10/scikit-fastapi.html

{!../../../docs_src/custom_response/tutorial004.py!}
```

In this example, the function `generate_html_response()` already generates and returns a `Response` instead of returning the HTML in a `str`.

By returning the result of calling `generate_html_response()`, you are already returning a `Response` that will override the default **FastAPI** behavior.