Design a high-throughput A/B Testing System
Last updated: November 15, 2025
Quick Overview
Design a high-throughput a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Vercel
November 15, 2025383
3
1,399 solved
Design a high-throughput a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from Vercel's Onsite tests whether you can reason about software design at a deep level. The interviewer expects discussion of maintainability, testability, and operational considerations.
What the Interviewer Expects
- Apply engineering principles to a realistic design scenario
- Discuss trade-offs between different approaches with concrete examples
- Demonstrate understanding of testability, maintainability, and extensibility
- Connect theoretical concepts to production engineering practices
- Discuss how the approach scales with team and codebase size
Key Topics to Cover
How to Approach This
- Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
- Choose data structures based on access patterns, not familiarity.
- Prefer immutable data and message passing over shared mutable state for concurrency.
- Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
- What are the security implications of this design?
- How would this design change if the team size doubled?
- How would you handle backward compatibility?
- What testing strategy would you use for this component?
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Core Design Principles
For designing a high-throughput A/B Testing System at Vercel, the core design principles to focus on include:
- SOLID Principles: Emphasizing the Single Responsibility Principle (SRP) ensures th...
Architecture
The architecture for the A/B testing system should be microservices-based, leveraging Vercel's serverless capabilities to handle millions of requests efficiently:
- API Gateway: Acts as the entr...
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