Design a A/B Testing for Zoom
Last updated: February 10, 2026
Quick Overview
Design a real-time a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Zoom
February 10, 20268
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4,314 solved
Design a real-time a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This is a common system design question asked during Technical Screen at Zoom. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Zoom values engineers who can think about scalability from day one.
What the Interviewer Expects
- Clearly define functional and non-functional requirements
- Propose a reasonable high-level architecture with core components
- Choose appropriate data storage solutions with basic justification
- Discuss basic scaling strategies (horizontal scaling, caching)
- Identify potential bottlenecks and suggest simple solutions
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 implement rate limiting to protect the system?
- How would you handle a region-wide outage?
- What monitoring and alerting would you set up on day one?
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Requirements
Functional Requirements:
- User Segmentation: Ability to segment users into different groups for A/B testing.
- Experiment Creation: Users should be able to create, manage, and delete A/...
Capacity Estimation
Assume Zoom has around 300 million active users:
- Daily Active Users: 300 million
- Requests for A/B testing per user: Assume 1 request per user per day for A/B testing.
- **Total Requests pe...
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