Building a Secure, Cost-Efficient Authentication System for Millions of Users

When a ride-hailing app’s daily logins soared to 12 million, SMS-based authentication became unsustainably expensive. The engineering team rebuilt the system with multi-channel login options — SMS, voice, WhatsApp, Facebook, and Google — tailored by region. By keeping funnels intact, simplifying architecture, and strengthening security (6-digit codes, device fingerprinting), they reduced authentication costs dramatically, maintained conversion rates, and scaled safely across 40 countries. The result: millions saved, lower fraud, and a faster, more user-friendly login experience.