260 million subscribers

Netflix serves 260 million subscribers across 190 countries. At peak — Friday evening in the US after a big series drop — it handles over 15% of all downstream internet traffic on the planet. That's not a metaphor. ISPs plan their capacity around Netflix's usage patterns.

The core tension

Video streaming has three competing constraints: quality (4K HDR requires 25 Mbps), availability (99.99% uptime = <53 min downtime/year), and scale (millions of concurrent streams). You cannot optimise all three naively — the architecture must be partitioned by responsibility.

Three distinct systems

We'll build Netflix as three interlocking systems: (1) the Playback Service + Adaptive Streaming Engine that gets video to the screen; (2) the upload and transcoding pipeline that prepares every title before it can stream; and (3) the Recommendation Service that drives 80% of what viewers watch.