Design a Feature Flag Service
Last updated: December 28, 2025
Quick Overview
Design a fault-tolerant feature flag system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Coinbase
December 28, 202599
5
2,280 solved
Design a fault-tolerant feature flag system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Software engineering fundamentals questions at Coinbase test your understanding of core CS concepts and their practical application. This System Design Round question evaluates how you apply engineering principles to build maintainable, scalable software.
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?
- What testing strategy would you use for this component?
- How would this design change if the team size doubled?
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Core Design Principles
For the Feature Flag Service at Coinbase, the core design principles that apply include Separation of Concerns, Single Responsibility Principle, and Fail-Fast Design.
- **Separation of C...
Architecture
The architectural approach for the Feature Flag Service at Coinbase will leverage a microservices architecture designed for high availability and fault tolerance.
- Microservices: Each microserv...
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