The Firebase Admin Node.js SDK allows you to integrate your own servers with Firebase Cloud Messaging (FCM). The Admin FCM API handles authenticating with Firebase servers on your behalf and grants you elevated privileges to send messages to your users and manage topic subscriptions.
The Admin Node.js SDK provides an API for sending messages to individual devices, device groups, and topics.
Manage topic subscriptions
The Admin Node.js SDK also provides an API for managing device subscriptions to topics.