This includes, for example:

* Email notifications sent after performing an action:
    * As connecting to an email server and sending an email tends to be "slow" (several seconds), you can return the response right away and send the email notification in the background.
* Processing data:

Now, there are some cases where you might want to have the **same schema for input and output**.

Probably the main use case for this is if you already have some autogenerated client code/SDKs and you don't want to update all the autogenerated client code/SDKs yet, you probably will want to do it at some point, but maybe not right now.

For example, you might want to try:

* <a href="https://speakeasy.com/editor?utm_source=fastapi+repo&utm_medium=github+sponsorship" class="external-link" target="_blank">Speakeasy</a>

---

If you just don't know, use normal `def`.

---

**Note**: You can mix `def` and `async def` in your *path operation functions* as much as you need and define each one using the best option for you. FastAPI will do the right thing with them.

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.

The benefit of raising an exception over returning a value will be more evident in the section about Dependencies and Security.

Keep in mind that this means that the whole contents will be stored in memory. This will work well for small files.

But there are several cases in which you might benefit from using `UploadFile`.

## File Parameters with `UploadFile` { #file-parameters-with-uploadfile }

Define a file parameter with a type of `UploadFile`:

<div style="text-align: right; margin-right: 10%;">Kabir Khan - <strong>Microsoft</strong> <a href="https://github.com/fastapi/fastapi/pull/26" target="_blank"><small>(ref)</small></a></div>

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"_We adopted the **FastAPI** library to spawn a **REST** server that can be queried to obtain **predictions**. [for Ludwig]_"

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code is a great way to give something back to the open source community. Before
you dig right into the code, there are a few guidelines that we need
contributors to follow so that we can have a chance of keeping on top of
things.

Some of the ideas are documented in the [Maven Wiki][maven-wiki]
which might be interesting to read and for further discussion.

Getting Started
---------------

        logger.debug(indent + artifact + " (not setting artifactScope to: " + ignoredScope + "; local artifactScope "
                + artifact.getScope() + " wins)");

        // TODO better way than static? this might hide messages in a reactor
        if (!ignoredArtifacts.contains(artifact)) {
            logger.warn("\n\tArtifact " + artifact + " retains local artifactScope '" + artifact.getScope()