The design of my application bootstrap consists of the /app/
directory which contains the api folder, allowing for a client folder where you may build the front end application using your technology stack of choice and within there consume the api. Alongside there is a /config/
folder where any global configurations must be defined, the application's API manifest is declared inside.
This mini framework is designed to work with Firebase and firebase-admin as a database service, keeping in mind that you could perfectly modify it as needed, and connect to something else (i.e. A Mongodb instance). For Firebase, you need the serviceAccountKey.json generated automatically by Firebase, in the admin, for this application management; this file goes to ./app/config/credentials/serviceAccountKey.json. Observation 1: The document is not included in the repo because of reasons. Observation 2: Firebase service account key has a long hashed name. Rename it to serviceAccountKey.json so the framework can pick it up, and work with the your firebase application.
Read the full article here.