I’ve been thinking a lot about real-time notifications lately because I recently faced a challenge in one of my projects where users needed instant updates without constant page refreshing. Traditional polling felt clunky and resource-heavy, while WebSockets seemed overkill for our one-way communication needs. That’s when I rediscovered Server-Sent Events—a simpler, more elegant solution that’s been hiding in plain sight. If you’re building applications that need to push updates to clients efficiently, stick with me as I walk through how to create a robust notification system using SSE, Redis, and TypeScript.

Server-Sent Events allow your server to send automatic updates to clients over a single HTTP connection. Think of it as a one-way street where data flows from server to browser without interruption. Did you know that SSE automatically handles reconnections if the connection drops? This built-in resilience makes it perfect for notifications where occasional missed messages are acceptable but reliability matters.

Let me show you how simple it is to set up a basic SSE endpoint. In your Node.js application with Express, you can create a route that initializes the connection and starts streaming events. The key is setting the right headers to tell the browser this is an event stream.

app.get('/notifications', (req, res) => {
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    'Connection': 'keep-alive'
  });
  
  // Send initial message
  res.write('data: Connected successfully\n\n');
});

On the client side, you can listen for these events using the EventSource API. But what happens when your user base grows and you need to send personalized notifications? That’s where Redis comes into play as a message broker.

Redis acts as the backbone for scaling your notification system. By using its pub/sub mechanism, you can broadcast messages to multiple connected clients efficiently. Imagine you have thousands of users online simultaneously—Redis helps manage those connections without overwhelming your server.

Here’s how you might integrate Redis to handle user-specific notifications. First, you’d set up a Redis client and subscribe to channels based on user IDs.

import Redis from 'ioredis';

const redis = new Redis();
const userConnections = new Map();

redis.subscribe('user:*', (err, count) => {
  if (err) console.error('Subscription failed');
});

redis.on('message', (channel, message) => {
  const userId = channel.split(':')[1];
  const connection = userConnections.get(userId);
  if (connection) {
    connection.write(`data: ${message}\n\n`);
  }
});

But how do you ensure that only authorized users receive their notifications? Authentication is crucial. You can middleware to verify users before establishing the SSE connection. When a request comes in, check their credentials and attach user information to the request object.

app.use('/notifications', authMiddleware);

function authMiddleware(req, res, next) {
  const token = req.headers.authorization;
  if (!token) return res.status(401).send();
  
  // Verify token and attach user
  req.user = { id: 'user123' };
  next();
}

Connection management becomes critical in production. You need to track active connections, handle disconnections gracefully, and clean up resources. Ever wondered what happens when a user closes their tab? Your server should detect that and remove their connection from memory.

Implementing heartbeat messages helps keep connections alive and detects dead ones. Every 30 seconds, send a ping to the client. If they don’t respond, you can close the connection.

setInterval(() => {
  userConnections.forEach((connection, userId) => {
    if (!connection.write('data: ping\n\n')) {
      userConnections.delete(userId);
    }
  });
}, 30000);

Performance optimization is another area where Redis shines. By offloading message distribution to Redis, your application server remains responsive. You can also use connection pooling and optimize your TypeScript code for better execution.

Testing your notification system ensures reliability. Write unit tests for your SSE utilities and integration tests that simulate multiple clients connecting and receiving messages. How would you simulate a sudden surge in traffic? Tools like Artillery can help load test your implementation.

Deploying to production involves setting up monitoring for connection counts, message throughput, and error rates. Services like Prometheus or Datadog can track these metrics, alerting you to issues before users notice.

Throughout this process, I’ve found that keeping code modular with TypeScript interfaces makes maintenance easier. Defining clear types for notifications and connections prevents bugs and improves developer experience.

interface Notification {
  id: string;
  userId: string;
  message: string;
  timestamp: Date;
}

const notification: Notification = {
  id: '1',
  userId: 'user123',
  message: 'Your order has shipped!',
  timestamp: new Date()
};

Building this system taught me that simplicity often beats complexity. SSE provides a straightforward path to real-time features without the overhead of more complex protocols. Have you considered how this approach could simplify your current projects?

I hope this guide helps you implement scalable real-time notifications in your applications. If you found this useful, please like and share this article with your network. I’d love to hear about your experiences or answer any questions in the comments below—let’s keep the conversation going!