Step 4: High-Level Architecture

The system has two jobs: collect every new article from thousands of outside sources, and show each user a feed of the articles that match what they follow. Reading a feed is ordinary serving. The hard work happens earlier, between the moment a publisher posts an article and the moment it sits in the right feeds.

We follow one example through the whole system. A wire service publishes "NASA sets a date for the next Moon landing". Maya follows the Science category and the entity NASA (an entity is a specific person, organization, or thing, like "NASA" or "Taylor Swift")