If you look at it, *path operation functions* are declared to be used whenever a *path* and *operation* matches, and then **FastAPI** takes care of calling the function with the correct parameters, extracting the data from the request.

Actually, all (or most) of the web frameworks work in this same way.

You never call those functions directly. They are called by your framework (in this case, **FastAPI**).

        with:
          # For discussion, see the first setup-java block.
          # The publish-snapshot workflow doesn't run tests, so we don't have to care which version Maven would select for that step.
          java-version: 25
          distribution: 'temurin'
          cache: 'maven'
          server-id: central
          server-username: CI_DEPLOY_USERNAME

## Mounting a **FastAPI** application { #mounting-a-fastapi-application }

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

### Top-level application { #top-level-application }

///

### What is "Mounting" { #what-is-mounting }

"Mounting" means adding a complete "independent" application in a specific path, that then takes care of handling all the sub-paths.

This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

It brings the same **developer experience** of building apps with FastAPI to **deploying** them to the cloud. 🎉

It will also take care of most of the things you would need when deploying an app, like:

* HTTPS
* Replication, with autoscaling based on requests
* etc.

# Sub-dependencies { #sub-dependencies }

You can create dependencies that have **sub-dependencies**.

They can be as **deep** as you need them to be.

**FastAPI** will take care of solving them.

## First dependency "dependable" { #first-dependency-dependable }

You could create a first dependency ("dependable") like:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

      throw new UnsupportedOperationException("test should not care about this");
    }

    @Override
    public long getDelay(TimeUnit unit) {
      throw new UnsupportedOperationException("test should not care about this");
    }

    @Override
    public int compareTo(Delayed other) {
      throw new UnsupportedOperationException("test should not care about this");
    }
  }

      throw new UnsupportedOperationException("test should not care about this");
    }

    @Override
    public long getDelay(TimeUnit unit) {
      throw new UnsupportedOperationException("test should not care about this");
    }

    @Override
    public int compareTo(Delayed other) {
      throw new UnsupportedOperationException("test should not care about this");
    }
  }

You can use multiple worker processes with the `--workers` CLI option with the `fastapi` or `uvicorn` commands to take advantage of **multi-core CPUs**, to run **multiple processes in parallel**.

You could use these tools and ideas if you are setting up **your own deployment system** while taking care of the other deployment concepts yourself.

But it is way more complex than that.

/// tip

If you are in a hurry or don't care, continue with the next sections for step by step instructions to set everything up with different techniques.

///

To **learn the basics of HTTPS**, from a consumer perspective, check [https://howhttps.works/](https://howhttps.works/).

Now, from a **developer's perspective**, here are several things to keep in mind while thinking about HTTPS: