Google is normally quite secretive about their search infrastructure but, in a break from tradition, they have revealed that a single search query on Google can consume the processing power of 1000 machines.
Google Fellow Jeff Dean, in a keynote talk at WSDM 2009, shared some numbers about Google’s impressive growth run from 1999 to 2009. According to Dean, while both search queries and processing power have gone up by a factor of 1000, latency has gone down from around 1000ms to 200ms. Crawler updates now take minutes compared to months in 1999.
Another significant change was the switch to holding the complete search index in memory, resulting in the use of 1000 machines to handle a single query compared to just 12 previously.
This revelation may be a bit embarrassing for Google, which has defended its ecological record in the past, claiming that a single Google query takes just 0.0003KWh of energy and that the Google datacenters are "the world’s most efficient."
Also see: How Google Works
This image of Google’s first production server is courtesy Jurvetson.