Design a geo-distributed A/B Testing System
Last updated: October 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.
Optiver
System Design
Software Engineer
Optiver
October 3, 2025Software Engineer
Technical Screen
System Design
Medium
85
10
3,901 solved
Design a geo-distributed a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Optiver 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
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
Security and authentication
High-level architecture and component design
Load balancing and horizontal scaling
Requirements gathering and capacity estimation
Consistency models and replication
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
- What would the deployment pipeline look like for this system?
- How would you handle a 10x increase in traffic overnight?
- What happens if one of your database nodes goes down?
- How would you migrate from a monolithic to a microservices architecture?
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Requirements
Functional Requirements
- User Segmentation: Ability to segment users based on geography, demographics, and behavior for targeted testing.
- Experiment Creation: Allow product managers...
Capacity Estimation
Back-of-Envelope Calculations
- User Base: Assume Optiver has 10 million active users globally.
- A/B Tests: Assume an average of 100 active A/B tests running concurrently.
- **Requ...
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