Design a A/B Testing for Notion

Last updated: September 5, 2025

Quick Overview

Design a multi-tenant a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Notion
System Design
Software Engineer
Notion
September 5, 2025
Software Engineer
Onsite
System Design
Easy

6

14

4,641 solved


Design a multi-tenant a/b testing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Notion asks this during the Onsite 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
  • 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
Partitioning and sharding strategies
Requirements gathering and capacity estimation
Caching strategies (local, distributed, CDN)
API design and rate limiting
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
  • How would you handle schema migrations with zero downtime?
  • What would the deployment pipeline look like for this system?
  • How would you implement rate limiting to protect the system?
  • How would you handle a 10x increase in traffic overnight?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For A/B Testing for Notion, key functional requirements include: what are...

Capacity Estimation

Estimate the scale to drive design decisions. Assume 100M DAU with an average of 10 actions per user per day = 1B requests/day ~ 12K QPS average, ~36K...


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