Design a URL Shortening Service
Last updated: August 2, 2025
Quick Overview
Design a high-throughput url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Capital One
System Design
Machine Learning Engineer
Capital One
August 2, 2025Machine Learning Engineer
Technical Screen
System Design
Medium
45
14
1,349 solved
Design a high-throughput url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Capital One 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
Partitioning and sharding strategies
Load balancing and horizontal scaling
Database selection and data modeling
Failure handling and fault tolerance
Monitoring, logging, and alerting
High-level architecture and component design
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 would you handle a region-wide outage?
- What monitoring and alerting would you set up on day one?
Practice a Similar Problem on Codemia
Solve a related problem with our interactive workspace, get AI feedback, and view detailed solutions.
Solve on CodemiaSample Answer
Requirements
Functional Requirements
- Shorten URL: The service should accept a long URL and return a shortened version.
- Redirect: The shortened URL should redirect to the original long URL when ac...
Capacity Estimation
Back-of-Envelope Calculations
- Expected Throughput: Assume an average of 1 million requests per day, translating to approximately 11.6 requests per second (QPS).
- Storage Requirements: A...
Submit Your Answer
Markdown supported