Scaling WhatsApp notifications to 10M messages daily

Sending millions of messages daily requires more than just calling an API in a loop. You must handle rate limits, avoid backpressure issues, manage queue prioritization, and process webhook callbacks at scale.

Concurrency and Webhook Backpressure

For every message sent, WhatsApp triggers multiple status events: Sent, Delivered, Read. If you broadcast 1 million notifications, your servers will receive 3 million incoming webhook hits within a short window.

To prevent crashing your primary web servers, do not process webhook payloads synchronously. Instead, route incoming webhook traffic directly into a fast queue system (such as Redis or RabbitMQ) and process them asynchronously using background workers.

Smart Load Balancing and Failover

At MSGTODAY, we use carrier priority routing. If a national gateway experiences latency spikes, our system detects the degradation within 3 seconds and shifts load to alternative nodes, guaranteeing zero message drops.

// Standard webhook response flow
app.post('/webhook', (req, res) => {
  // 1. Immediately return 200 OK to WhatsApp
  res.sendStatus(200);
  
  // 2. Push payload to Redis queue for background workers
  queue.push(req.body);
});