Design A/B Testing Infrastructure for microservices
Last updated: August 29, 2025
Quick Overview
Design a low-latency a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Coinbase
August 29, 2025236
3
2,694 solved
Design a low-latency a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This is a common system design question asked during System Design Round at Coinbase. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Coinbase values engineers who can think about scalability from day one.
What the Interviewer Expects
- Clearly define functional and non-functional requirements
- Propose a reasonable high-level architecture with core components
- Choose appropriate data storage solutions with basic justification
- Discuss basic scaling strategies (horizontal scaling, caching)
- Identify potential bottlenecks and suggest simple solutions
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 handle a 10x increase in traffic overnight?
- How would you handle schema migrations with zero downtime?
- What monitoring and alerting would you set up on day one?
- What happens if one of your database nodes goes down?
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Requirements
Functional Requirements
- A/B Test Creation: Allow product managers to define and create A/B tests, specifying control and variant groups, and associated metrics.
- User Assignment: Impl...
Capacity Estimation
To estimate capacity:
- User Base: Assume Coinbase has 50 million active users.
- A/B Test Participation: Assume each user participates in an average of 2 A/B tests per month.
- Requests: ...
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