Mobile Push Notification Architecture

Push notifications are the most powerful and most abused channel in mobile engineering. Well-designed notifications drive engagement — a timely alert about a package delivery or a price drop on a watched item creates genuine value. Poorly designed notifications — spam, irrelevant updates, middle-of-the-night pings — get your app uninstalled.

Architecture

Push Notification Pipeline:

Your Backend → Push Delivery Service → Platform Gateway → Device

Step 1: Server decides to send notification
  Trigger: Business event (order shipped, message received)
  Personalization: User preferences, timezone, quiet hours
  Targeting: Specific user/device or segment

Step 2: Push delivery service
  ┌──────────────────────────────────────────────┐
  │  Push Service (Firebase, OneSignal, etc.)     │
  │                                              │
  │  Token management:                           │
  │    Device registers → receives push token    │
  │    Token stored in your backend              │
  │    Tokens refresh → need re-registration     │
  │                                              │
  │  Platform routing:                           │
  │    iOS tokens → APNs (Apple Push Service)    │
  │    Android tokens → FCM (Firebase Cloud Msg) │
  │    Web tokens → Web Push (VAPID)             │
  └──────────────────────────────────────────────┘

Step 3: Platform gateway delivers to device
  APNs: Requires .p8 auth key or .p12 certificate
  FCM: Requires service account or API key
  
Step 4: Device receives and displays
  Foreground: Handle in-app (banner, in-app message)
  Background: System notification tray
  Killed: System wakes app briefly for processing

Implementation

class NotificationService:
    """Production notification service with best practices."""
    
    def send_notification(self, user_id: str, notification: dict):
        """Send a smart, personalized push notification."""
        
        user = self.get_user(user_id)
        
        # 1. Check user preferences
        if not user.notifications_enabled:
            return {"status": "skipped", "reason": "notifications_disabled"}
        
        category = notification["category"]
        if category not in user.enabled_categories:
            return {"status": "skipped", "reason": f"category_{category}_disabled"}
        
        # 2. Respect quiet hours
        user_time = self.get_local_time(user.timezone)
        if self.is_quiet_hours(user_time, notification.get("priority", "normal")):
            # Queue for delivery after quiet hours
            self.schedule_for_later(user_id, notification, 
                                   after=user.quiet_hours_end)
            return {"status": "scheduled", "deliver_at": user.quiet_hours_end}
        
        # 3. Rate limiting
        recent_count = self.get_recent_notification_count(
            user_id, window_hours=24
        )
        if recent_count >= user.daily_limit:
            return {"status": "throttled", "reason": "daily_limit_reached"}
        
        # 4. Send to all user devices
        devices = self.get_user_devices(user_id)
        results = []
        for device in devices:
            if device.platform == "ios":
                result = self.send_apns(device.token, notification)
            elif device.platform == "android":
                result = self.send_fcm(device.token, notification)
            results.append(result)
        
        return {"status": "sent", "devices": len(results)}

Anti-Patterns

Push notifications are a privilege granted by the user. Every notification that does not provide genuine value erodes that trust. Design for relevance, respect for attention, and measurable engagement.