You will see the automatic API docs, including the paths from all the submodules, using the correct paths (and prefixes) and the correct tags:

<img src="/img/tutorial/bigger-applications/image01.png">

## Include the same router multiple times with different `prefix`

You can also use `.include_router()` multiple times with the *same* router using different prefixes.

        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {},
        "webhooks": {
            "new-subscription": {
                "post": {
                    "summary": "New Subscription",
                    "description": "When a new user subscribes to your service we'll send you a POST request with this\ndata to the URL that you register for the event `new-subscription` in the dashboard.",

    response = client.get("/openapi.json")
    assert response.status_code == 200
    assert response.json() == {
        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/items/": {
                "get": {
                    "summary": "Read Items",
                    "operationId": "read_items_items__get",
                    "parameters": [
                        {

    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/users/": {
                "get": {
                    "summary": "Read Users",
                    "operationId": "read_users_users__get",
                    "responses": {

    assert response.status_code == 200, response.text
    assert response.json() == {
        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/schema_extra/": {
                "post": {
                    "summary": "Schema Extra",
                    "operationId": "schema_extra_schema_extra__post",
                    "requestBody": {

You would probably do this just once, the first time, when setting everything up.

!!! tip
    This Domain Name part is way before HTTPS, but as everything depends on the domain and the IP address, it's worth mentioning it here.

### DNS

Now let's focus on all the actual HTTPS parts.

First, the browser would check with the **DNS servers** what is the **IP for the domain**, in this case, `someapp.example.com`.

In particular, this may be a good alternative to logic in a middleware.

For example, if you want to read or manipulate the request body before it is processed by your application.

!!! danger
    This is an "advanced" feature.

    If you are just starting with **FastAPI** you might want to skip this section.

## Use cases

Some use cases include:

=== "Python 3.8+"

    ```Python hl_lines="1  4"
    {!> ../../../docs_src/python_types/tutorial008.py!}
    ```

This means:

* The variable `prices` is a `dict`:
    * The keys of this `dict` are of type `str` (let's say, the name of each item).
    * The values of this `dict` are of type `float` (let's say, the price of each item).

#### Union

!!! warning "Deprecated"
    This tutorial is deprecated and will be removed in a future version.

You can also use <a href="https://github.com/encode/databases" class="external-link" target="_blank">`encode/databases`</a> with **FastAPI** to connect to databases using `async` and `await`.

It is compatible with:

* PostgreSQL
* MySQL
* SQLite

* The API checks that `username` and `password`, and responds with a "token" (we haven't implemented any of this yet).
    * A "token" is just a string with some content that we can use later to verify this user.
    * Normally, a token is set to expire after some time.
        * So, the user will have to log in again at some point later.