How did Google Instant become Faster with 5-7X More Results Pages?

We don't have a lot of details on how Google pulled off their technically very impressive Google Instant release, but in Google Instant behind the scenes, they did share some interesting facts:
- Google was serving more than a billion searches per day.
- With Google Instant they served 5-7X more results pages than previously.
- Typical search results were returned in less than a quarter of second.
- A team of 50+ worked on the project for an extended period of time.
Although Google is associated with muscular data centers, they just didn't throw more server capacity at the problem, they worked smarter too. What were their general strategies?