```Dockerfile
RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt
```

The file with the package requirements **won't change frequently**. So, by copying only that file, Docker will be able to **use the cache** for that step.

And then, Docker will be able to **use the cache for the next step** that downloads and install those dependencies. And here's where we **save a lot of time**. ✨ ...and avoid boredom waiting. 😪😆

When deploying applications you will probably want to have some **replication of processes** to take advantage of **multiple cores** and to be able to handle more requests.

As you saw in the previous chapter about [Deployment Concepts](concepts.md), there are multiple strategies you can use.

 */
@Deprecated(since = "4.0.0")
public interface ModelSource2 extends ModelSource {
    /**
     * Returns model source identified by a path relative to this model source POM. Implementation <strong>MUST</strong>
     * be able to accept <code>relPath</code> parameter values that
     * <ul>
     * <li>use either / or \ file path separator</li>
     * <li>have .. parent directory references</li>

The original dependency could be used in a *path operation function*, a *path operation decorator* (when you don't use the return value), a `.include_router()` call, etc.

FastAPI will still be able to override it.

///

Then you can reset your overrides (remove them) by setting `app.dependency_overrides` to be an empty `dict`:

```Python
app.dependency_overrides = {}
```

/// tip

* Running on startup
* Restarts
* Replication (the number of processes running)
* Memory
* Previous steps before starting

We'll see how they would affect **deployments**.

In the end, the ultimate objective is to be able to **serve your API clients** in a way that is **secure**, to **avoid disruptions**, and to use the **compute resources** (for example remote servers/virtual machines) as efficiently as possible. 🚀

     * local repository manager needs to be configured to make session be able to create session instance.
     *
     * @return SessionBuilder configured with minimally required things for "Maven-based resolution". At least LRM must
     * be set on builder to make it able to create session instances.
     */
    @Override
    public SessionBuilder get() {

```Python
say_hi(name=None)  # This works, None is valid 🎉
```

The good news is, in most cases, you will be able to simply use `|` to define unions of types:

```python
def say_hi(name: str | None):
    print(f"Hey {name}!")
```

Keep in mind that custom proprietary headers can be added [using the `X-` prefix](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers).

### Enable Keycloak Admin REST API support

Before being able to authenticate against the Admin REST API using a client_id and a client_secret you need to make sure the client is configured as it follows:

- `account` client_id is a confidential client that belongs to the realm `{realm}`

 *     return createExpensiveGraph(key);
 *   }
 * };
 * LoadingCache<Key, Graph> cache = CacheBuilder.newBuilder().build(loader);
 * }
 *
 * <p>Since this example doesn't support reloading or bulk loading, if you're able to use lambda
 * expressions it can be specified even more easily:
 *
 * {@snippet :
 * CacheLoader<Key, Graph> loader = CacheLoader.from(key -> createExpensiveGraph(key));
 * }
 *
 * @author Charles Fry