Read data from Firebase database as an admin

Let's assume that you want:

1. Only the admin to read from the database in Firebase.
2. Prevent the users to delete data as well.

You'll need to write the following rules in Firebase:

javascript
{
    "rules": {
        ".read":  false,
        ".write": "!data.exists()"
    }
}

Even if ".read": false, the admin has always access to read from the database.

Trigger a function after data creation

If you want to trigger a function after a user creates new data, you can use the onCreate() function. If you combine this function with the admin SDK, you'll be able to read from the database:

javascript
const functions  = require('firebase-functions');
const admin      = require('firebase-admin');

// Initialize as admin
admin.initializeApp();

// We read the data from /orders/{orderId} as admins
exports.newDataCreation = functions.database.ref('/orders/{orderId}').onCreate(async (snapshot, context) => {       
    
    // If you try to read data such as
    // const { tee, mode, size } = snapshot.val();
    // You'll get permission denied error. Rules will prevent you to read data as a normal user 
    
    // You'll need to read data as admin
    let data = await admin.database().ref('/orders/' + context.params.orderId).once('value');
    
    const { tee, model, size } = await data.val();
    
});

Note: to get the full path of the new data, you can use the context.params object.