Guide to Implement Push Notification Engine

Push Notification Engine: Architecture, Implementation, and Roadmap

Introduction

Push notifications play a crucial role in modern applications by enabling real-time communication with users. A well-architected Push Notification Engine ensures reliable, scalable, and personalized notifications across multiple channels such as Email, SMS, In-App, and Social Media.

This blog provides an in-depth guide on designing and implementing a Push Notification System, covering:

• Business Services & Notification Gateway
• Notification Distribution & Routing
• Channels & Delivery Mechanisms
• Tracing, Analytics & User Preferences
• Tech Stack Recommendations
• Implementation Roadmap & Timeline

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1. Business Services

1.1 Service Responsibilities

Business services are responsible for triggering notifications in response to user actions.

✅ Single Event Notifications (E.g., Order Confirmed, Payment Received)

✅ Batch Notifications (E.g., Monthly Statement, Flight Reminders)

✅ Publishing Events to Message Brokers (E.g., Azure Service Bus, Kafka)

Implementation Example

public class OrderService
{
    private readonly IMessageBroker _messageBroker;

    public OrderService(IMessageBroker messageBroker)
    {
        _messageBroker = messageBroker;
    }

    public async Task NotifyOrderConfirmation(Order order)
    {
        var eventMessage = new NotificationEvent
        {
            UserId = order.UserId,
            NotificationType = NotificationType.OrderConfirmed,
            Payload = new { OrderId = order.Id, Amount = order.Amount }
        };

        await _messageBroker.PublishAsync("OrderConfirmed", eventMessage);
    }
}

📌 Source of Information: E-commerce Order Management System, Payment Service

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2. Notification Gateway

The Notification Gateway acts as an entry point for all notification events and ensures decoupling between business services and the notification system.

Responsibilities

• Ingests Events from Message Brokers
• Validates & Transforms Data into a Standard Format
• Routes to the Next Processing Stage

Implementation Example

public class NotificationGateway
{
    private readonly INotificationService _notificationService;

    public async Task HandleNotificationEvent(NotificationEvent eventMessage)
    {
        if (!ValidateEvent(eventMessage))
            return;

        var standardizedMessage = TransformToStandardFormat(eventMessage);
        await _notificationService.ProcessNotificationAsync(standardizedMessage);
    }
}

📌 Source of Information: Message Broker (Azure Service Bus, Kafka)

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3. Notification Distribution

This layer is responsible for prioritizing, validating, and scheduling notifications before delivery.

3.1 Validation

• User existence check
• Channel preference validation
• Required fields verification (e.g., Template ID, Message content)

Implementation Example

if (!userExists || !IsValidChannel(notification))
{
    LogError("Invalid notification details");
    return;
}

📌 Source of Information: User Service, Preference Database

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3.2 Scheduler

Handles future notifications (e.g., Reminders, Offers).

✅ Stores scheduled notifications in SQL/NoSQL DB

✅ Processes & triggers notifications at scheduled time

Implementation Example

public class NotificationScheduler
{
    private readonly ISchedulerStore _schedulerStore;
    private readonly INotificationService _notificationService;

    public async Task ProcessScheduledNotifications()
    {
        var pendingNotifications = await _schedulerStore.GetPendingNotificationsAsync();

        foreach (var notification in pendingNotifications)
        {
            await _notificationService.SendNotificationAsync(notification);
        }
    }
}

📌 Source of Information: Database (SQL/NoSQL)

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3.3 Priority Handling

High Priority: OTPs, Payment Failure

Medium Priority: Order Updates

Low Priority: Promotional Messages

Implementation Example

notification.Priority = notification.Type switch
{
    NotificationType.OTP => Priority.High,
    NotificationType.OrderUpdate => Priority.Medium,
    _ => Priority.Low
};

📌 Source of Information: Notification Type Definitions

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3.4 Template Management

✅ Stores & fetches templates dynamically

✅ Applies placeholders with real-time user data

Example Template

{
    "templateId": "OrderConfirmation",
    "content": "Hello {UserName}, your order #{OrderID} has been confirmed!"
}

📌 Source of Information: SQL/NoSQL Template Store

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4. Notification Router

Uses Message Queues (RabbitMQ, Azure Service Bus) to route notifications based on the delivery channel.

✅ Decouples processing

✅ Prioritizes & batches notifications

Implementation Example

public class NotificationRouter
{
    public async Task RouteNotification(NotificationMessage message)
    {
        var queue = GetQueueForChannel(message.Channel);
        await _queueService.EnqueueAsync(queue, message);
    }
}

📌 Source of Information: User Preferences, Channel Configurations

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5. Channels

Each channel has a dedicated service to handle notification delivery.

5.1 Email

✅ Uses SendGrid, AWS SES

✅ Fallback Mechanism for failed emails

await _emailService.SendEmailAsync(user.Email, subject, message);

5.2 SMS

✅ Uses Twilio, Nexmo

✅ Retries on failure

await _smsService.SendSmsAsync(user.Phone, message);

5.3 In-App

✅ Real-time via SignalR

✅ Stores notifications for offline users

await _inAppService.SendNotificationAsync(user.Id, message);

📌 Source of Information: Third-Party APIs (SendGrid, Twilio, SignalR, WebSockets)

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6. Notification Tracing & Analytics

✅ Logs event ingestion, processing & delivery

✅ Tracks key metrics (Delivery Rate, Open Rate, Click-Through Rate)

Implementation Example

var log = new NotificationLog
{
    NotificationId = Guid.NewGuid(),
    Status = "Delivered",
    Timestamp = DateTime.UtcNow
};
await _logService.SaveLogAsync(log);

📌 Source of Information: Logging Service, Analytics Store

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7. User Preferences Management

Allows users to opt in/out of notifications.

✅ Preference Storage (SQL/NoSQL)

✅ Validation Before Sending

Example Storage Format

{
  "UserId": "12345",
  "Preferences": {
    "Email": true,
    "SMS": false,
    "InApp": true
  }
}

📌 Source of Information: User Settings Database

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8. Tech Stack Recommendations

Component	Technology
Backend	.NET Core, ASP.NET Web API
Message Broker	Azure Service Bus, RabbitMQ, Kafka
Database	SQL Server, Cosmos DB, MongoDB
Cache	Redis
Notification Channels	SendGrid, Twilio, SignalR
Analytics & Monitoring	Azure Monitor, Grafana, Power BI

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9. Workflow Example

1️⃣ Order Service publishes OrderConfirmed event

2️⃣ Notification Gateway validates & transforms event

3️⃣ Router directs message to Email Queue

4️⃣ Email Worker sends notification via SendGrid

5️⃣ Logs & Analytics capture delivery status

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10. Implementation Roadmap

Phase	Tasks	Timeline
Phase 1	Setup database, core schema, and preferences API	2 weeks
Phase 2	Implement Notification Gateway & Message Broker	2 weeks
Phase 3	Develop Notification Router & Channels (Email/SMS)	3 weeks
Phase 4	Add In-App Delivery, Scheduler, and Batch Processing	2 weeks
Phase 5	Implement Template Management, Logging & Analytics	2 weeks

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Conclusion

A well-designed Push Notification Engine ensures scalability, reliability, and user personalization. By following this architecture and roadmap, you can build an efficient, event-driven notification system for your application.

• For more detail, get this document Push Notification Engine