Step 5: High-Level Design

The system has two jobs: show each user a home page of recommended rows the moment they open the app, and learn from everything they watch so that tomorrow's rows are better. The design separates the two. The expensive work, training models and scoring titles, happens offline, hours before the user arrives, and the request path only reads the stored answer.

We follow one user through both jobs. On Friday night, Priya finishes the last episode of a sci-fi series on her TV. On Saturday morning, she opens Netflix on her phone