Recommendation algorithm

The recommendation pipeline has four steps:

1. Candidate sourcing - Fetch the best tweets from different recommendation sources
2. Ranking - Rank tweets such that the most relevant ones appear first in the feed.
3. Filtering - Apply heuristics and filters to create a balanced and diverse feed.
4. Mixing non-tweet content like Ads, Follow Recommendations, and Onboarding prompts.

The recommendation pipeline runs 5 billion times per day and completes in under 1.5 seconds on average.