Caffeine is Google’s new web indexing system which now provides 50 percent fresher results and includes more web content than ever before. This means, every time you search using Google, results are updated 50% quicker and web content such as videos, photos, news stories and tweets are included to help provide you the most relevant result to your search term, effectively improving your web searching experience.
Google’s Caffeine has actually been in effect for the past 6 months but wasn’t officially released until last month. You may have noticed minor changes to Google during this period such as videos from YouTube to regular updated news stories being included in the search results, though Caffeine was still being refined.
Before Caffeine, Google’s indexing system was based on layers. Some layers were refreshed faster than others while the main layer would be updated every couple of weeks. However, to refresh a layer of Google’s old index, Google would have to analyse the web in its entirety, which meant a significant delay between finding a page and making it appear within their index. With Caffeine, Google can now analyse the web in small portions and update their search index on a more constant basis, allowing new information and websites to be added into their index faster than ever.
Google has expressed Caffeine was built for both the near future and beyond, allowing it to scale with the addition of new information whilst delivering a whole wide range of websites, videos, tweets and much more quicker.Source: https://googleblog.blogspot.com/2010/06/our-new-search-index-caffeine.html