Design a geo-distributed Authentication System
Last updated: April 4, 2026
Quick Overview
Design a geo-distributed authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Netflix
April 4, 202655
14
1,101 solved
Design a geo-distributed authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Netflix asks this during the Technical Screen to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.
What the Interviewer Expects
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- How would you handle a 10x increase in traffic overnight?
- How would you implement rate limiting to protect the system?
- How would you handle a region-wide outage?
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Requirements
Functional Requirements
- User Authentication: Support user login, logout, and registration across multiple geographic regions.
- Session Management: Maintain and validate user sessions, i...
Capacity Estimation
Assuming Netflix has 200 million subscribers and an average of 50% login frequency per day:
- Daily Logins: 200M * 50% = 100M logins/day.
- Peak Hour Load: Assuming peak usage happens in 1 hou...
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