Design a video streaming platform

Setting

You're building the upload-to-playback pipeline for a video platform: creators upload raw video, it needs to become smoothly playable on phones, laptops, and TVs over widely varying network conditions, worldwide.

The ask

Design the system that ingests an uploaded video, prepares it for playback, and serves it to viewers with minimal buffering regardless of their connection.

Constraints & scale

• ~500K uploads/day, average 10 minutes; ~1B playback-hours/month across the globe
• Playback must adapt to the viewer's bandwidth in real time (no manual quality selection required) and start within ~1–2 s of pressing play
• Processing an upload into playable form should complete in well under real time (a 10-minute upload ready in a few minutes, not a few minutes per minute of footage)
• Popular new uploads can spike to millions of views within hours; unpopular long-tail content still needs to be servable on demand years later
• Content must be served from edge locations near the viewer, not from one origin per request

What a strong answer covers

Requirements → estimates (storage, encoding fan-out, egress) → high-level diagram (ingest/transcode pipeline, storage, CDN delivery, adaptive playback) → 1–2 deep dives → trade-offs. Likely probes: the transcoding pipeline's parallelism, adaptive bitrate mechanics, and cold-start vs. hot-content caching at the edge.

Graded on

Every session — this problem included — is scored against the same 10-dimension senior/staff rubric: