send push notifications from backend

To send push notifications from a backend, you generally use a push provider or platform-specific APIs.

Common options

1) Web Push

For browsers, use:

• Service Workers
• Push API
• VAPID keys
• A backend library like web-push

Example flow:

1. Frontend asks permission and subscribes the device/browser.
2. Frontend sends the subscription object to your backend.
3. Backend stores subscriptions.
4. Backend sends push payloads to those subscriptions.

2) Mobile push notifications

For iOS/Android, most backends use a push service:

• Firebase Cloud Messaging (FCM) for Android, web, and iOS
• Apple Push Notification service (APNs) for iOS
• Or a provider like OneSignal, Expo, etc.

Typical flow:

1. App gets a device push token.
2. App sends token to backend.
3. Backend stores token.
4. Backend sends notification via FCM/APNs/provider API.

Example: sending via FCM from backend

If you're using Firebase Cloud Messaging, your backend can call FCM with the device token.

Node.js example

import admin from "firebase-admin";
import serviceAccount from "./serviceAccountKey.json" assert { type: "json" };

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
});

async function sendNotification(token) {
  const message = {
    token,
    notification: {
      title: "Hello",
      body: "You have a new message",
    },
    data: {
      type: "chat",
      chatId: "123",
    },
  };

  const response = await admin.messaging().send(message);
  console.log("Sent:", response);
}

Python example

import firebase_admin
from firebase_admin import credentials, messaging

cred = credentials.Certificate("serviceAccountKey.json")
firebase_admin.initialize_app(cred)

message = messaging.Message(
    notification=messaging.Notification(
        title="Hello",
        body="You have a new message",
    ),
    token="DEVICE_TOKEN_HERE",
)

response = messaging.send(message)
print("Sent:", response)

Best practices

• Store and refresh device tokens.
• Remove invalid/expired tokens.
• Send notifications asynchronously from a job queue.
• Keep payloads small.
• Use topic messaging or segments if you need to target many users.

If you want, I can show you:

• a Node.js backend example
• a Python backend example
• FCM setup steps
• iOS/Android token handling
• web push with service workers