System Design Interview Questions - Medium
Medium-level system design interview questions covering complex distributed systems.
Q1: Design Twitter/X.
Answer:
Requirements
- Post tweets (280 chars)
- Follow/unfollow users
- Timeline (home feed)
- Search tweets
- Trending topics
- 500M users, 100M DAU
Architecture
Tweet Flow
Timeline Generation
Fanout Strategies:
Database Schema
Q2: Design Instagram.
Answer:
Requirements
- Upload photos/videos
- Follow users
- Feed with posts
- Like/comment
- Stories (24h expiry)
- 1B users, 500M DAU
Architecture
Upload Flow
Feed Ranking
Q3: Design Uber/Lyft.
Answer:
Requirements
- Match riders with drivers
- Real-time location tracking
- ETA calculation
- Pricing
- Payment processing
- 100M users, 10M drivers
Architecture
Matching Algorithm
Location Tracking
Geospatial Indexing
Q4: Design Netflix.
Answer:
Requirements
- Stream videos
- Recommendations
- Search content
- Multiple devices
- 200M subscribers
- 4K streaming
Architecture
Video Encoding Pipeline
Recommendation System
Adaptive Streaming
Q5: Design YouTube.
Answer:
Requirements
- Upload videos
- Stream videos
- Comments/likes
- Subscriptions
- Search
- 2B users, 1B hours watched daily
Architecture
Upload Pipeline
View Count System
Summary
Medium system design patterns:
- Twitter: Fanout strategies, timeline generation
- Instagram: Media processing, feed ranking
- Uber: Geospatial indexing, real-time matching
- Netflix: Adaptive streaming, ML recommendations
- YouTube: Video transcoding, distributed CDN
All designs emphasize scalability, real-time processing, and user experience.
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