Mock Interviewer
Ask Coach
Tap a question to start, or type your own below.
Netflix System Design
Visual Problem Diagram
Scenario
Prime-time Friday: 20M streams start within an hour, each needing the right bitrate chunk from the nearest edge while your encoding pipeline is still finishing the 4K ladder for a new release. Buffering for 3 seconds loses viewers; a bad recommendation row loses the next hour—CDN placement and adaptive streaming dominate the interview.
Design a video streaming platform like Netflix where users browse a catalog, receive personalized recommendations, and watch content with minimal buffering. Production success depends on async transcoding, globally distributed caches, and adaptive bitrate clients—not a monolithic video file per watch.
You should support upload/encode, catalog browse, personalized home, smooth playback with quality adaptation, and resume across devices. Be ready to explain CDN strategy, encoding ladders, manifest/segment model, and how recommendations stay off the play-start critical path.
Constraints
Catalog browse, video upload and transcode, adaptive streaming playback, recommendations, resume, profiles, DRM hooks
< 2 s start playback p95, minimal rebuffering, 99.99% availability for playback, global delivery
200M subscribers, ~20M concurrent peak streams, petabytes catalog, millions of encodes in flight, read-heavy CDN
Stages ahead
Log in to start practicing
Preview the problem below. Sign in to start your timed session, save progress, and use the AI coach.