Design a Rate Limiting Service
Last updated: October 15, 2025
Quick Overview
Design a scalable rate limiting system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Mastercard
October 15, 2025100
5
265 solved
Design a scalable rate limiting system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Mastercard asks this during the System Design Round to assess your depth in software engineering. They want to see understanding of design patterns, system architecture, and the trade-offs involved in different technical approaches.
What the Interviewer Expects
- Apply engineering principles to a realistic design scenario
- Discuss trade-offs between different approaches with concrete examples
- Demonstrate understanding of testability, maintainability, and extensibility
- Connect theoretical concepts to production engineering practices
- Discuss how the approach scales with team and codebase size
Key Topics to Cover
How to Approach This
- Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
- Choose data structures based on access patterns, not familiarity.
- Prefer immutable data and message passing over shared mutable state for concurrency.
- Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
- How would you document this for other engineers?
- How would you handle backward compatibility?
- What testing strategy would you use for this component?
- How would this design change if the team size doubled?
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Core Design Principles
For the rate limiting service at Mastercard, the core design principles that apply are:
- Separation of Concerns: This principle ensures that our rate limiting logic is decoupled from the applic...
Architecture
The architecture for the rate limiting service at Mastercard will consist of the following components:
- API Gateway: Acts as the entry point for all incoming requests and handles initial rate l...
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