Design a large-scale A/B Testing Platform
Last updated: February 12, 2026
Quick Overview
Design a event-driven a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Goldman Sachs
System Design
Product Manager
Goldman Sachs
February 12, 2026Product Manager
Onsite
System Design
Medium
246
12
3,752 solved
Design a event-driven a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Goldman Sachs typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.
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
Partitioning and sharding strategies
Message queues and async processing
Consistency models and replication
Security and authentication
High-level architecture and component design
Requirements gathering and capacity estimation
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 region-wide outage?
- What monitoring and alerting would you set up on day one?
- How would you implement rate limiting to protect the system?
- How would you migrate from a monolithic to a microservices architecture?
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Requirements
Functional Requirements:
- User Segmentation: Ability to define user segments for testing (e.g., by demographics, behavior).
- Experiment Creation: Users can create, modify, and delete e...
Capacity Estimation
Back-of-the-Envelope Calculations:
- Expected Requests: Assume 5 million active users, each generating 10 requests per day related to A/B tests.
- Total daily requests = 5 million users * ...
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