Design a multi-tenant Authentication System
Last updated: November 26, 2025
Quick Overview
Design a multi-tenant authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Zoom
System Design
Software Engineer
Zoom
November 26, 2025Software Engineer
Onsite
System Design
Hard
39
11
2,874 solved
Design a multi-tenant authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Zoom 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
Caching strategies (local, distributed, CDN)
Requirements gathering and capacity estimation
Partitioning and sharding strategies
Load balancing and horizontal scaling
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 happens if one of your database nodes goes down?
- How would you handle schema migrations with zero downtime?
- What would the deployment pipeline look like for this system?
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Requirements
Functional Requirements:
- User Authentication: Support for email/password, SSO (OAuth, SAML), and MFA.
- Tenant Management: Each tenant should have its own user base, with the ability t...
Capacity Estimation
Capacity Estimates:
- User Base: Assume 10 million tenants, with an average of 1000 users per tenant. Total users = 10 billion.
- Authentication Requests: Assume peak request rate of 1000 ...
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