Design a URL Shortening Service
Last updated: May 28, 2026
Quick Overview
Design a scalable url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
PlanetScale
May 28, 20261
8
3,852 solved
Design a scalable url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This fundamentals question from PlanetScale's System Design Round tests whether you can reason about software design at a deep level. The interviewer expects discussion of maintainability, testability, and operational considerations.
What the Interviewer Expects
- Design a complex system component applying multiple engineering principles
- Reason about system-level trade-offs: performance, reliability, developer experience
- Discuss advanced patterns: event sourcing, CQRS, distributed transactions
- Address cross-cutting concerns: observability, security, backward compatibility
- Demonstrate depth in both theoretical foundations and practical implementation
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
- What testing strategy would you use for this component?
- How would you measure the performance of this component in production?
- What are the security implications of this design?
- How would you handle backward compatibility?
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Core Design Principles
For the URL shortening service, key design principles include Separation of Concerns, Scalability, and Consistency vs. Availability.
- Separation of Concerns: Each component of the ...
Architecture
The architecture of the URL shortening service is designed as a microservices system, with the following components:
- API Gateway: Handles incoming requests and routes them to the respective se...
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