Design a Feature Flag Service
Last updated: July 6, 2025
Quick Overview
Design a geo-distributed feature flag system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Optiver
July 6, 20251
6
3,598 solved
Design a geo-distributed feature flag system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Optiver asks this during the Onsite to assess your understanding of the full ML lifecycle. They want to see how you translate a business problem into an ML objective, design the feature pipeline, and plan for model monitoring and retraining.
What the Interviewer Expects
- Design the full ML lifecycle from data collection to model monitoring
- Address cold start, exploration/exploitation, and model freshness
- Discuss multi-objective optimization and ranking systems
- Plan for model debugging, fairness, and bias mitigation
- Design the feature store and training pipeline for scale
- Address model versioning, canary deployments, and rollback strategies
- Discuss the data flywheel and long-term system evolution
Key Topics to Cover
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 would you ensure fairness and reduce bias in the model?
- How would you handle the cold start problem?
- How would you handle a 10x increase in prediction requests?
Practice a Similar Problem on Codemia
Solve a related problem with our interactive workspace, get AI feedback, and view detailed solutions.
Solve on CodemiaSample Answer
Requirements
Functional Requirements
- Feature Flag Creation/Management: Ability for product teams to create, edit, and delete feature flags in real-time.
- User Segmentation: Support for targeting spe...
Capacity Estimation
Assuming Optiver has approximately 10 million active users and expects about 100 feature flags being toggled with an average of 1 request per user per feature flag per day:
- Daily Requests: 10,0...
Submit Your Answer
