Design a A/B Testing for HubSpot
Last updated: January 10, 2026
Quick Overview
Design a distributed a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
HubSpot
January 10, 202634
4
3,682 solved
Design a distributed a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from HubSpot's Technical Screen 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
- Explain the concept clearly with a practical example
- Discuss when and why to apply this principle
- Identify common mistakes and anti-patterns
- Compare with alternative approaches
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
- How would this design change if the team size doubled?
- What testing strategy would you use for this component?
- How would you document this for other engineers?
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Core Design Principles
For designing an A/B testing system at HubSpot, the key design principles to focus on include Separation of Concerns, Scalability, and Observability.
- Separation of Concerns: This ...
Architecture
The proposed architecture for HubSpot's A/B testing system is a Microservices Architecture that uses a combination of API Gateway, Load Balancers, and Distributed Databases.
- **API G...
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