Netflix is a subscription video-on-demand service: a curated catalog of movies and shows that members browse, get recommendations for, and stream on any device. Unlike a user-upload platform, content arrives in bulk from studios and is processed offline, long before anyone presses play.
Two facts shape the entire design:
- Every title is pre-encoded offline into an adaptive-bitrate (ABR) ladder — dozens of resolution/bitrate/codec variants, chopped into small segments — so the player can switch quality on the fly.
- Playback is overwhelmingly read-heavy and bandwidth-dominated. Tens of millions of concurrent streams mean hundreds of terabits per second of egress. No origin datacenter can serve that; the bytes must come from caches inside ISPs (Open Connect).
So the hard parts aren't uploads or transactions — they're massive CDN/edge delivery and a recommendation pipeline that decides what every member sees. This is the canonical "read-heavy delivery at planet scale" interview.