System design interview question
Design a Distributed Session Store and Real-Time User State Management System (Like Auth0 at Scale)
Design a globally distributed session management system that handles 200M active users with 50K concurrent session creation/validation requests per second, sub-100ms latency requirements, and must support session invalidation across multiple geographies within 500ms. The system must maintain user authentication state, handle graceful session expiration, support concurrent device sessions per user, detect anomalous login patterns in real-time, and provide strong consistency for security-critical operations while allowing eventual consistency for non-critical metadata. Sessions span multiple datacenters across North America, Europe, and Asia-Pacific with regional preference for latency but global reachability for compliance.
Practice this question step by step with an AI interviewer that reviews your requirements, your architecture and your trade-offs, and scores the design.