Design a high-throughput Authentication System
Last updated: August 23, 2025
Quick Overview
Design a high-throughput authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Rippling
August 23, 2025171
7
1,396 solved
Design a high-throughput authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Rippling asks this during the Onsite 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
- Drive the design discussion proactively with minimal interviewer guidance
- Perform detailed capacity estimation and use it to inform design decisions
- Design for global scale with multi-region deployment and data consistency
- Deep dive into 2-3 critical components with implementation-level detail
- Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
- Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
- Propose a phased rollout plan from MVP to full-scale system
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 do you ensure data consistency across multiple services?
- How would you handle a region-wide outage?
- How would you implement rate limiting to protect the system?
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Requirements
Functional Requirements
- User Authentication: Support login via email/password, multi-factor authentication (MFA), and OAuth providers (Google, Facebook).
- Session Management: Maintain...
Capacity Estimation
Assuming Rippling has approximately 1 million active users:
- Daily Requests: 10 million requests/day translates to about 115 requests/second.
- User Activity: If each user logs in 5 times a d...
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