85: Reel Friends: Building Social Discovery that Scales to Billions
About this episode
The episode discusses the engineering challenges behind the Friend Bubbles feature on Facebook Reels.
You've probably spotted those little circles of your friends' faces popping up on Facebook Reels. They look simple enough, but building them was a proper engineering challenge. In this episode, Pascal chats to Joseph and Subasree about Friend Bubbles, a feature that surfaces which of your close friends have been watching and reacting to the same Reels as you. We get into the details of how prefetching keeps things snappy without wrecking scroll performance, why the team's ML model had to move from survey-based friend rankings to real-time interaction signals, and the surprising discovery that showing fewer bubbles actually made the whole feature click. If you've ever underestimated a "simple" feature, this one's for you. Got feedback? Send it to us on Threads ( https://threads.net/@metatechpod ), Instagram ( https://instagram.com/metatechpod ) and don't forget to follow our host Pascal ( https://mastodon.social/@passy , https://threads.net/@passy_ ). Fancy working with us? Check out https://www.metacareers.com/ . Links https://engineering.fb.com/2026/03/18/ml-applications/friend-bubbles-enhancing-social-discovery-on-facebook-reels/…
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