How would you design a tiny URL service like bit.ly?
A high-level system design question focusing on scalability, hashing, and database choices. It assesses architectural decision-making skills.
Why Interviewers Ask This
This is a standard system design interview question used to evaluate how candidates handle real-world scaling issues. Interviewers want to see if you can design a solution that is fast, reliable, and scalable. They look for discussions on collision resolution, database sharding, and load balancing. It also tests your ability to balance trade-offs between storage costs and lookup speed.
How to Answer This Question
Start by estimating scale (QPS, storage size). Propose a hashing strategy (e.g., Base62 encoding of a counter or MD5 hash). Discuss the database schema for mapping short URLs to long ones. Mention caching layers like Redis for hot links. Address potential issues like hash collisions and how to handle them. Finally, discuss redundancy and failover mechanisms for high availability.
Key Points to Cover
- Use Base62 encoding for compact IDs
- Implement a distributed ID generator
- Utilize caching for read-heavy workloads
- Design for horizontal scalability
Sample Answer
To design a URL shortener, I would first generate a unique ID for each new URL. I could use a distributed counter or a hash of the original URL. To make it human-readable, I'd encode this ID using Base62. The short URL w…
Common Mistakes to Avoid
- Ignoring collision handling strategies
- Overlooking the need for a caching layer
- Focusing too much on the frontend UI
- Not discussing database partitioning
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