Design a large-scale URL Shortening Platform
Last updated: September 9, 2025
Quick Overview
Design a fault-tolerant url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
SpaceX
September 9, 20255
12
1,957 solved
Design a fault-tolerant url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at SpaceX 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
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 migrate from a monolithic to a microservices architecture?
- How do you ensure data consistency across multiple services?
- How would you optimize costs as the system scales?
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Requirements
Functional Requirements
- URL Shortening: Users can input a long URL and receive a shortened version.
- Redirection: When a user accesses the shortened URL, they are redirected to the orig...
Capacity Estimation
Assuming SpaceX's URL shortening platform serves 10 million users, let's estimate the capacity:
- Requests per second (QPS): If each user generates ~5 requests per day, that's approximately:
...
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