LinkedIn rebuilt its feed for 400M users, making it faster with new FollowFeed system

LinkedIn spent twenty months replacing its old feed system, which was built on a generic search platform that became too costly to maintain. The new system, called FollowFeed, assembles user feeds on-demand from hundreds of millions of individual content timelines rather than storing pre-built feeds. This 'pull' model is five times faster, holds twenty times more data, and runs on half the servers compared to the old infrastructure. The engineering team achieved these gains by running scoring directly on the data storage nodes and using optimized storage technology like RocksDB. The rebuild was driven by the need to manage surging membership and data volumes at a sustainable cost.