Designing a Reliable Notification System for 1M+ Users (Push, SMS, Email)
Isaac Ojerumu
In fintech, notifications are not a “nice-to-have” feature. They’re part of the product’s trust layer. If a user transfers money and doesn’t get a confirmation, they panic. If an OTP arrives 3 minutes late, login fails. If price alerts come twice, users lose confidence fast. At small scale, sending notifications feels simple: Application → Twilio/SendGrid → Done But once you’re dealing with millions of users, multiple channels, retries, provider outages, and traffic spikes… notification systems