Design a A/B Testing Service
Last updated: August 3, 2025
Quick Overview
Design a geo-distributed a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Shopify
August 3, 2025141
5
1,013 solved
Design a geo-distributed a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from Shopify's System Design Round 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
- How would this design change if the team size doubled?
- What are the security implications of this design?
- How would you document this for other engineers?
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Core Design Principles
For designing the A/B Testing Service at Shopify, we will apply the SOLID principles to ensure our system is maintainable and extensible:
- Single Responsibility Principle: Each component (e...
Architecture
The proposed architecture for the A/B Testing Service will follow a microservices architecture pattern, deployed across geo-distributed data centers to ensure low latency and high availability:
-...
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