There're two posts on Facebook's engineering blog that discuss this (they're from 2013 when they first started working on the feature): https://www.facebook.co

There're two posts on Facebook's engineering blog that discuss this (they're from 2013 when they first started working on the feature): https://www.facebook.com/notes/facebook-engineering/under-the-hood-indexing-and-ranking-in-graph-search/10151361720763920 https://www.facebook.com/notes/facebook-engineering/under-th... https://www.facebook.com/notes/facebook-engineering/under-the-hood-building-posts-search/10151755593228920 https://www.facebook.com/notes/facebook-engineering/under-th...