More on the Caffeine graphic referenced earlier
To keep up with the evolution of the web and to meet rising user expectations, we've built Caffeine. The image below illustrates how our old indexing system worked compared to Caffeine:
Our old index had several layers, some of which were refreshed at a faster rate than others; the main layer would update every couple of weeks. To refresh a layer of the old index, we would analyze the entire web, which meant there was a significant delay between when we found a page and made it available to you.
With Caffeine, we analyze the web in small portions and update our search index on a continuous basis, globally. As we find new pages, or new information on existing pages, we can add these straight to the index. That means you can find fresher information than ever before—no matter when or where it was published.
See the full post for more details