Caffeine: The next-generation architecture for Google's web search

It's the first step in a process that will let us push the envelope on size, indexing speed, accuracy, comprehensiveness and other dimensions. The new infrastructure sits "under the hood" of Google's search engine, which means that most users won't notice a difference in search results. But web developers and power searchers might notice a few differences, so we're opening up a web developer preview to collect feedback.

visit the web developer preview of Google's new infrastructure at http://www2.sandbox.google.com/ and try searches there.

Source: http://googlewebmastercentral.blogspot.com/2009/08/help-test-some-next-generation.html