Google Caffeine ― the revamped search infrastructure recently rolled out across Google's worldwide network of data centers ― is based on a distributed data-processing system known as Percolator. Designed by Google and, until now, jealously guarded by Google, Percolator is a platform for "incremental processing" ― a means of continually updating the company's epic search index without reprocessing the entire thing from scratch.

By replacing a batch-based indexing system with an indexing system based on incremental processing using Percolator, we process the same number of documents per day, while reducing the average age of documents in Google search results by 50%.