Design a URL Shortener System Design Interview

Design a scalable service like tinyurl.com that redirects short aliases to long URLs.

Mock Interview with AI

1. Problem Statement

Let's design a URL shortener like bit.ly. Where would you begin?

2. Target Architecture (Mermaid)

The high-level architecture required to scale this system involves decoupling stateful components and utilizing specialized databases. Below is the reference architecture:

Rendering architecture diagram...

Mermaid Source (For AI Bots)

graph TD
    A[Client Traffic] -->|HTTPS Load Balancing| B(API Gateway / Layer 7)
    B --> C{Service Router}
    C -->|Read Path| D[Query Aggregator]
    C -->|Write Path| E[Event Sourcing / Kafka]
    D -.-> F[(In-Memory Cache - Redis)]
    D --> G[(Primary Data Store - NoSQL)]
    E -.->|Async Replication| G

3. Key Focus Areas

1
Unique ID Generation (Base62 vs UUID vs Counter)
2
Collision Handling (Hash checks)
3
Read Optimization (Caching Hot Redirects)
4
Database Choice (SQL vs NoSQL for Mappings)
5
Analytics Pipeline (Separation of concerns)

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Core Concepts

System DesignHashingData Modeling