Step 1: System Definition and Goals

When a major company announces a product, hundreds of outlets report it within the hour. A reader who follows that company wants one feed with the story near the top, shown once rather than three hundred times, and a phone alert if they asked for one. A news aggregator produces that feed. This case study designs the backend of one, similar to Google News.

An aggregator does not write news. It collects articles from external publishers, such as newspapers, broadcasters, and blogs, and presents them in a single personalized feed. Each user's feed follows that user's interests