```python exec
import reflex as rx
```

# Backend API Routes

In addition to your frontend app, Reflex also uses a FastAPI backend to serve your app.

To add additional endpoints to the backend API, you can use `app.add_api_route` and add a route that returns JSON.

```python
async def api_test(item_id: int):
    return \{"my_result": item_id}

app = rx.App()
app.api.add_api_route("/items/\{item_id}", api_test)
```

Now you can access the endpoint at `localhost:8000/items/23` and get the result.

This is useful for creating a backend API that can be used for purposes other than your Reflex app.

## Reserved Routes

Some routes on the backend are reserved for the runtime of Reflex, and should not be overriden unless you know what you are doing.

## Ping

`localhost:8000/ping/`: You can use this route to check the health of the backend.

The expected return is `"pong"`.

## Event

`localhost:8000/_event`: the frontend will use this route to notify the backend that an event occurred.

```md alert error
# Overriding this route will break the event communication
```

## Upload

`localhost:8000/_upload`: This route is used for the upload of file when using `rx.upload()`.