Build a distributed Authentication Pipeline
Last updated: March 26, 2026
Quick Overview
Design a distributed authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Google
System Design
Software Engineer
Software Engineer
Technical Screen
System Design
Medium
103
15
4,589 solved
Design a distributed authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Google 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
- 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
Database selection and data modeling
Message queues and async processing
Monitoring, logging, and alerting
Failure handling and fault tolerance
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 region-wide outage?
- What monitoring and alerting would you set up on day one?
- What would the deployment pipeline look like for this system?
- How would you handle schema migrations with zero downtime?
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Requirements
Functional Requirements:
- User Authentication: Support user login through various methods (email/password, OAuth, etc.).
- Multi-Factor Authentication (MFA): Provide an option for addit...
Capacity Estimation
Back-of-Envelope Calculations:
- User Base: Assume 1 billion users with 50% active daily users.
- Daily Requests: requests/day.
- *...
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