Design A/B Testing Infrastructure for mobile apps

Last updated: March 27, 2026

Quick Overview

Design a scalable a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Jump Trading
Software Engineering Fundamentals
Software Engineer
Jump Trading
March 27, 2026
Software Engineer
System Design Round
Software Engineering Fundamentals
Medium

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Design a scalable a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Jump Trading asks this during the System Design Round to assess your depth in software engineering. They want to see understanding of design patterns, system architecture, and the trade-offs involved in different technical approaches.

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
Version control and branching strategies
API design and RESTful conventions
Testing strategies (unit, integration, e2e)
System observability and debugging
Design patterns (Factory, Observer, Strategy, etc.)
How to Approach This
  1. Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
  2. Choose data structures based on access patterns, not familiarity.
  3. Prefer immutable data and message passing over shared mutable state for concurrency.
  4. Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
  • How would you measure the performance of this component in production?
  • How would you document this for other engineers?
  • How would this design change if the team size doubled?
  • What testing strategy would you use for this component?
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Sample Answer
Core Principles

Start by identifying which engineering principles are most relevant: **SOLID Principles**: Single Responsibility (one reason to change), Open/Closed ...

Design Approach

**API Design**: Define clear interfaces before implementation. Use RESTful conventions for HTTP APIs. Version your APIs from the start. Return meaning...


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