If Google were the United States government, the data that streams onto Nicholas Fox’s laptop every day would be classified as top secret.

Mr. Fox is among a small group of Google employees who keep a watchful eye on the vital signs of one of the most successful and profitable businesses on the Internet. The number of searches and clicks, the rate at which users click on ads, the revenue this generates — everything is tracked hour by hour, compared with the data from a week earlier and charted.

“You can see very, very quickly if anything is amiss,” said Mr. Fox, director of business product management at Google.

Mr. Fox and his “ads quality” team can also quickly see whether something is working particularly well. His group’s mission, to constantly fine-tune Google’s ad delivery system, has one overriding objective: show users only the ads they are most likely to be interested in and click on.