Google Instant, said Mayer, saves an average of two to five seconds per query. Applied to the billions queries Google processes per day, that translates to 350 million hours of users' time per year.
Such theoretical time savings remains a secondary consideration. Google is trying to make the search experience better, to take it beyond mere keyword call and response. Google Instant builds upon the company's search autocompletion technology, which tries to predict queries based on what the user has typed, by actually executing the top suggested query and returning results with each keystroke.
That represents a significant increase in the load handled by Google's data centers. Each letter typed represents a search that must be processed. When the project was first conceived there were doubts it would be affordable. Google couldn't simply absorb the cost of handling 20 times its current query volume.
But Google engineer Ben Gomes said that as more Googlers contributed to the project, enough optimizations were developed to allow Google Instant to work within Google's infrastructure growth plans.
"I feel sure that this is the future direction of search," declared Gomes.
The impact of this new direction in search on search advertising remains to be seen. Mayer suggested that Google's ad serving wasn't likely to change a lot, apart from the company's decision to treat a pause of three seconds or more as an ad impression.
Google Instant will be made available to U.S. users of Chrome, Firefox, Safari, and IE 8 on Wednesday. To use the service, one must be signed in to one's Google Account. In coming weeks, Google expects to roll the service out in the U.K., France, Italy, Germany, Spain, and Russia.
Mayer said that Google plans to make Google Instant available worldwide in the months ahead. For users in China, where search suggestions are blocked because they might point people to politically sensitive information, Google Instant is likely to be available through the company's Hong Kong search site.
Google plans to make Google Instant available on mobile devices in a few months.
Users who don't like the idea of Google predicting their queries can turn Google Instant off if they wish. But Google predicts that most users won't bother.