Up to now, you have been declaring the parts of the request that you need with their types.

Taking data from:

* The path as parameters.
* Headers.
* Cookies.
* etc.

And by doing so, **FastAPI** is validating that data, converting it and generating documentation for your API automatically.

But there are situations where you might need to access the `Request` object directly.

///

## Order the parameters as you need { #order-the-parameters-as-you-need }

/// tip

This is probably not as important or necessary if you use `Annotated`.

///

Let's say that you want to declare the query parameter `q` as a required `str`.

And you don't need to declare anything else for that parameter, so you don't really need to use `Query`.

OdHOim9+
-----END PRIVATE KEY-----
```

Recommendations
---------------

Typically servers need a held certificate plus a chain of intermediates. Servers only need the
private key for their own certificate. The chain served by a server doesn't need the root
certificate.

The trusted roots don't need to be the same for client and server when using client authentication.

## Caveat { #caveat }

If you need to perform heavy background computation and you don't necessarily need it to be run by the same process (for example, you don't need to share memory, variables, etc), you might benefit from using other bigger tools like <a href="https://docs.celeryq.dev" class="external-link" target="_blank">Celery</a>.

    own the intellectual property, then you'll need to sign an [individual
    CLA][]. Please include your GitHub username.
  - If you work for a company that wants to allow you to contribute your work,
    then you'll need to sign a [corporate CLA][].

You generally only need to submit a CLA once, so if you've already submitted
one (even if it was for a different project), you probably don't need to do it
again.

Use the `TestClient` object the same way as you do with `httpx`.

Write simple `assert` statements with the standard Python expressions that you need to check (again, standard `pytest`).

{* ../../docs_src/app_testing/tutorial001_py39.py hl[2,12,15:18] *}

/// tip

Notice that the testing functions are normal `def`, not `async def`.

This can be very useful for setting up **resources** that you need to use for the whole app, and that are **shared** among requests, and/or that you need to **clean up** afterwards. For example, a database connection pool, or loading a shared machine learning model.

## Use Case { #use-case }

<abbr title="A utility/system to store computed/generated values, to reuse them instead of computing them again.">"cache"</abbr> and pass it to all the "dependants" that need it in that specific request, instead of calling the dependency multiple times for the same request.

In an advanced scenario where you know you need the dependency to be called at every step (possibly multiple times) in the same request instead of using the "cached" value, you can set the parameter `use_cache=False` when...

{* ../../docs_src/query_params_str_validations/tutorial002_py310.py hl[7] *}

As in this case (without using `Annotated`) we have to replace the default value `None` in the function with `Query()`, we now need to set the default value with the parameter `Query(default=None)`, it serves the same purpose of defining that default value (at least for FastAPI).

So:

```Python
q: str | None = Query(default=None)
```

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <!--
    Some tests need reflective access to the internals of these packages. It is only the
    tests themselves and not the code being tested that needs that access, though there's no
    obvious way to ensure that.

    We could consider arranging things so that only the tests we know need this would get
    the add-opens. Right now that doesn't seem worth the effort, though.