Build a low-latency Authentication Pipeline
Last updated: May 4, 2026
Quick Overview
Design a low-latency authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
OpenAI
System Design
Software Engineer
OpenAI
May 4, 2026Software Engineer
Technical Screen
System Design
Hard
141
14
726 solved
Design a low-latency authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at OpenAI typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.
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
Consistency models and replication
Caching strategies (local, distributed, CDN)
Security and authentication
Message queues and async processing
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?
- What would the deployment pipeline look like for this system?
- What monitoring and alerting would you set up on day one?
- How would you optimize costs as the system scales?
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Requirements
Functional Requirements
- User Authentication: Support for email/password, OAuth2, and API token-based authentication.
- Multi-Factor Authentication (MFA): Optional security layer for us...
Capacity Estimation
Back-of-Envelope Calculations
- Peak Requests: 10 million requests/hour translates to roughly 2,778 requests/second.
- Data Size: Each authentication request carries user credentials (e.g....
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