Immediate update of site-map index in google, shouldn't that be impossible?

Ckeck out http://www.blocket.se/goteborg?ca=15

Look at the first ad.

Copy the headline, and paste it into google, and also write 'blocket' after the headline in google, now search.

You will see it finds the ad right开发者_Python百科 away.

How come?

Does googles crawlers really update their index that fast?

Or is it just because you entered that search string that google quickly updates its index and returns the results?

Thanks

I will tag this php, mysql etc because usually you guys know these kind of things!

It's not immediate. Google does crawl some sites a lot more often than other sites, but it's never immediate.