I will show you some of the main concepts you should probably keep in mind when deploying a **FastAPI** application (although most of it applies to any other type of web application).

cookies and headers), and will put them in the final response that contains the value you returned, filtered by any `response_model`.

You can also declare the `Response` parameter in dependencies, and set the status code in them. But keep in mind that the last one to be set will win....

And as the `Response` can be used frequently to set headers and cookies, **FastAPI** also provides it at `fastapi.Response`.

///

## Custom Headers

Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

/// tip

Prefer to use the `Annotated` version if possible.

///

```Python hl_lines="7"
{!> ../../docs_src/path_params_numeric_validations/tutorial002.py!}
```

////

But keep in mind that if you use `Annotated`, you won't have this problem, it won't matter as you're not using the function parameter default values for `Query()` or `Path()`.

//// tab | Python 3.9+

```Python hl_lines="10"

## Server Machine and Server Program

There's a small detail about names to keep in mind. 💡

The word "**server**" is commonly used to refer to both the remote/cloud computer (the physical or virtual machine) and also the program that is running on that machine (e.g. Uvicorn).

Just keep in mind that when you read "server" in general, it could refer to one of those two things.

Then set Cookies in it, and then return it:

```Python hl_lines="10-12"
{!../../docs_src/response_cookies/tutorial001.py!}
```

/// tip

Keep in mind that if you return a response directly instead of using the `Response` parameter, FastAPI will return it directly.

```Python
q: str | None = None
```

But the `Query` versions declare it explicitly as being a query parameter.

/// info

Keep in mind that the most important part to make a parameter optional is the part:

```Python
= None
```

or the:

```Python
= Query(default=None)
```

* If you are feeling too generous, you can try to **create an example** like that yourself, just based on the description of the problem. Just keep in mind that this might take a lot of time and it might be better to ask them to clarify the problem first.

### Suggest solutions

* After being able to understand the question, you can give them a possible **answer**.

But when checking benchmarks and comparisons you should keep the following in mind.

## Benchmarks and speed

When you check the benchmarks, it is common to see several tools of different types compared as equivalent.

## Check the Docs

You can see the defined cookies in the docs UI at `/docs`:

<div class="screenshot">
<img src="/img/tutorial/cookie-param-models/image01.png">
</div>

/// info

Have in mind that, as **browsers handle cookies** in special ways and behind the scenes, they **don't** easily allow **JavaScript** to touch them.