Video Streaming Platform
System design for video player with adaptive streaming and offline support
Design a video streaming platform (Netflix, YouTube) with adaptive bitrate, subtitles, and offline downloads.
R - Requirements
Key Questions:
- Adaptive bitrate? (yes, for varying network)
- Subtitles? (multiple languages)
- Playback speed? (0.5x, 1x, 1.5x, 2x)
- Offline downloads? (yes, for mobile)
- Live streaming? (yes/no)
- Recommendations? (yes, personalized)
Common Answers:
- Adaptive streaming (HLS/DASH)
- Multiple subtitle languages
- Offline downloads for mobile
- Personalized recommendations
A - Architecture
Video Playback Flow:
Streaming Architecture:
Architecture Decisions:
- HLS/DASH for adaptive streaming - Adjust quality based on network
- CDN strategy (multiple regions, edge caching) - Low latency, high availability
- Client-side player (video.js, hls.js) - Handle streaming protocol
- Offline storage (IndexedDB for downloads) - Play offline on mobile
Relevant Content:
- Asset Optimization - Video optimization
- Offline-First Architecture - Downloads
D - Data Model
State Management:
- Playback state (position, quality, speed)
- Watch history (local + server)
- Recommendations (personalized)
- Offline downloads (IndexedDB)
Caching:
- Video segments (CDN caching)
- Metadata (video info, subtitles)
- Watch history (localStorage + server)
Relevant Content:
- Persistence Strategies - Watch history
- Network-Aware Components - Adaptive quality
I - Interface
Features:
- Video player controls (play, pause, seek)
- Quality selector (auto, 360p, 720p, 1080p, 4K)
- Subtitle selector (languages)
- Playback speed selector
- Progress bar with chapters
- Keyboard shortcuts (space, arrows)
- Fullscreen support
Accessibility:
- Keyboard navigation
- Screen reader support
- Captions/subtitles
- High contrast mode
Relevant Content:
- Keyboard Shortcuts - Player controls
- Accessible Animations - Player animations
O - Optimizations
Performance:
- Adaptive bitrate (adjust quality based on network)
- Video preloading (next video, segments)
- CDN optimization (edge caching, multiple regions)
- Bandwidth detection (choose initial quality)
Network:
- Network-aware quality (adjust based on connection)
- Buffering strategy (preload ahead, pause on slow)
- Connection pooling (reuse connections)
Offline:
- Download management (queue, resume, delete)
- Storage optimization (compress, delete watched)
Relevant Content:
- Network-Aware Components - Adaptive quality
- Connection Pooling - Connection reuse
- Asset Optimization - Video compression
Implementation Checklist
- Adaptive streaming (HLS/DASH)
- Quality selector (auto, manual)
- Subtitle support (multiple languages)
- Playback speed control
- Keyboard shortcuts
- Watch history (local + server)
- Offline downloads (IndexedDB)
- Network-aware quality
- CDN optimization
- Recommendations (personalized)
Common Pitfalls
❌ Fixed quality → Poor experience on slow networks
✅ Adaptive bitrate based on network speed
❌ No offline support → Can't watch without internet
✅ Download to IndexedDB, play offline
❌ No preloading → Users wait for next video
✅ Preload next video, buffer ahead
❌ Poor buffering → Stuttering playback
✅ Smart buffering strategy, network-aware