Finally Google has announced that new search index Caffeine is completed.
Today, we're announcing the completion of a new web indexing system called Caffeine. Caffeine provides 50 percent fresher results for web searches than our last index, and it's the largest collection of web content we've offered. Whether it's a news story, a blog or a forum post, you can now find links to relevant content much sooner after it is published than was possible ever before.
Some background for those of you who don't build search engines for a living like us: when you search Google, you're not searching the live web. Instead you're searching Google's index of the web which, like the list in the back of a book, helps you pinpoint exactly the information you need. (Here's a good explanation of how it all works.)
Read more at their blog: New Search Index: Caffeine