How Grab Built An Authentication System for 180+ Million Users

Grab transformed their fragmented authentication system serving 180+ million users by adopting OpenID Connect (OIDC) and implementing Dex, an open-source federated identity provider. The solution unified authentication across internal and external applications, replacing multiple custom OAuth implementations with a standardized approach. Key features include token delegation for service-to-service communication, multi-IdP failover for high availability, and single sign-on capabilities. This centralized system improved security, reduced administrative overhead, and provided a consistent user experience across Grab's ecosystem of ride-hailing, payments, and delivery services.