This one sprawled in every direction fast.
Start by clarifying requirements and scale (e.g., 1B+ videos, upload/playback rates, global distribution) before diving into high-level design. Then walk through the end-to-end pipeline: upload, transcoding, storage, metadata, CDN delivery, and playback, making key trade-offs explicit (e.g., consistency vs. availability, cost vs. latency).
Pro tip: Emphasize the importance of a content delivery network (CDN) and adaptive bitrate streaming for playback at scale, and discuss how you'd handle hot videos vs. long-tail content differently to optimize cost and performance.
Ask about expected upload volume, playback QPS, geographic distribution, latency targets, and consistency needs. Establish assumptions like 1B+ videos, 100M daily active users, and global access.
Sketch the main components: upload service, transcoding pipeline, object storage, metadata DB, CDN, and playback service. Explain how they interact and the data flow from upload to playback.
Detail the transcoding pipeline (e.g., chunked upload, parallel transcoding, multiple resolutions), storage tiering (hot vs. cold), and metadata sharding. Discuss how to handle failures and retries.
Explain how videos are served via CDN with adaptive bitrate streaming (HLS/DASH), caching strategies, and how to handle viral videos. Discuss pre-fetching and edge caching.
Discuss trade-offs: consistency vs. availability for metadata, cost vs. performance for storage tiers, and push vs. pull CDN models. Address scaling bottlenecks and monitoring.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.