How would you design a video streaming platform like YouTube?

Upload pipeline: client upload -> transcoding service (multiple resolutions, formats), thumbnail generation, metadata extraction, CDN distribution. Storage: blob storage for videos, CDN for delivery, database for metadata. Streaming: adaptive bitrate (HLS/DASH), CDN edge servers, origin shield. Features: recommendations (ML service), search (Elasticsearch), comments, likes, subscriptions. Scale: read-heavy (cache metadata), geographic distribution, hot video caching. Transcoding: distributed workers, priority queues. Analytics: view counts (eventually consistent counters), watch time. Monetization: ad insertion service.