Design a large-scale Feature Flag Platform
Last updated: May 25, 2026
Quick Overview
Design a real-time feature flag system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Coinbase
System Design
Software Engineer
Coinbase
May 25, 2026Software Engineer
Technical Screen
System Design
Hard
32
8
4,513 solved
Design a real-time feature flag system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Coinbase asks this during the Technical Screen to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.
What the Interviewer Expects
- Drive the design discussion proactively with minimal interviewer guidance
- Perform detailed capacity estimation and use it to inform design decisions
- Design for global scale with multi-region deployment and data consistency
- Deep dive into 2-3 critical components with implementation-level detail
- Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
- Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
- Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
API design and rate limiting
High-level architecture and component design
Requirements gathering and capacity estimation
Security and authentication
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- How do you ensure data consistency across multiple services?
- How would you optimize costs as the system scales?
- What would the deployment pipeline look like for this system?
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Requirements
Functional Requirements
- Feature Flag Management: Ability to create, update, and delete feature flags through a user-friendly interface.
- Real-time Evaluation: Immediate availability o...
Capacity Estimation
Back-of-Envelope Calculations
- User Base: Assume Coinbase has 100 million users globally.
- Feature Flags: Assume an average of 10 feature flags per user (1 billion evaluations).
- **R...
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