```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. 😪😆

 * should use the type safe {@link #putInstance}.
 *
 * <p>Also, if caller suppresses unchecked warnings and passes in an {@code Iterable<String>} for
 * type {@code Iterable<Integer>}, the map won't be able to detect and throw type error.
 *
 * <p>Like any other {@code Map<Class, Object>}, this map may contain entries for primitive types,
 * and a primitive type and its corresponding wrapper type may map to different values.
 *

///

/// 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.

If you go to the **API docs UI** at `/docs` you will be able to see the **documentation** for cookies for your *path operations*.

	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	l, err := lc.Listen(ctx, "tcp", net.JoinHostPort(host, port))
	if err != nil {
		return err
	}

	// As we are able to listen on this network, the port is not in use.
	// Close the listener and continue check other networks.
	return l.Close()

/// tip

The "PATCH" is the last number, for example, in `0.2.3`, the PATCH version is `3`.

///

So, you should be able to pin to a version like:

```txt
fastapi>=0.45.0,<0.46.0
```

Breaking changes and new features are added in "MINOR" versions.

/// tip

 */
@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>

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.

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. 🚀

```Python
from .routers.items import router
from .routers.users import router
```

the `router` from `users` would overwrite the one from `items` and we wouldn't be able to use them at the same time.

So, to be able to use both of them in the same file, we import the submodules directly:

{* ../../docs_src/bigger_applications/app_an_py310/main.py hl[5] title["app/main.py"] *}