HOW X DECIDES WHAT 550 MILLION USERS SEE

Summary from the TLDR Dev newsletter

X's feed algorithm, which determines what 550 million users see through a component-based pipeline, was recently open-sourced. The pipeline has sources like Thunder (for in-network posts) and Phoenix (for discovery), which feed candidates into a system of hydrators, filters, and multi-stage scorers. Posts are evaluated based on eighteen predicted engagement probabilities, weighted, and adjusted for author diversity and whether they are from followed accounts.