Design a URL Shortening for Twitter/X
Last updated: December 8, 2025
Quick Overview
Design a low-latency url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Twitter/X
December 8, 202525
5
1,611 solved
Design a low-latency url shortening system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This is a common system design question asked during System Design Round at Twitter/X. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Twitter/X values engineers who can think about scalability from day one.
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 optimize costs as the system scales?
- What monitoring and alerting would you set up on day one?
- What would the deployment pipeline look like for this system?
- How would you implement rate limiting to protect the system?
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Requirements
Functional Requirements
- Shorten URLs: Users should be able to submit a long URL and receive a shortened version.
- Redirects: When a shortened URL is accessed, it should redirect to th...
Capacity Estimation
Assuming Twitter/X has approximately 400 million daily active users and each user generates an average of 5 shortened URLs a day:
- Daily Requests: 400 million users * 5 URLs = 2 billion shorten...
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