Reel Friends: Building Social Discovery that Scales to Billions

What this post added

This post details the engineering behind the 'Friend Bubbles' feature for Reels, which highlights Reels watched and reacted to by friends. It discusses the evolution of the underlying machine learning model, platform-specific behaviors (iOS vs. Android), and a key discovery that enabled the feature's success. The post emphasizes the technical depth required for seemingly simple features and their scaling to billions of users.