Design a Rate Limiting Service
Last updated: December 28, 2025
Quick Overview
Design a event-driven rate limiting system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Two Sigma
December 28, 2025277
4
4,224 solved
Design a event-driven rate limiting system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Two Sigma 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
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 monitoring and alerting would you set up on day one?
- How would you migrate from a monolithic to a microservices architecture?
- How do you ensure data consistency across multiple services?
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Requirements
Functional Requirements:
- The system should allow clients to set rate limits on specific actions (e.g., API calls, event submissions).
- It should track the number of requests made by each ...
Capacity Estimation
Assuming Two Sigma expects to handle 1 million clients, each making an average of 10 requests per second.
- Total Requests per Second:
1,000,000 clients * 10 requests/client = 10,000,000 req...
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