How can they be that fast?

there are a couple of areas where Flickr's speed (seems to me) is just amazing, and wanted to share those:

Last night I wanted to upgrade to a Pro account, but ended up relying of friend to pay for the upgrade via PayPal... and I was talking with him over Skype at the same time. I felt just shocked to see the "Pro" logo on my account withing seconds (and I mean it, low single digit number of seconds)... that was amazingly fast payment processing. So fast that even a cash payment seems soooo slow.

And then today I finally bother to go start correcting typos or basic spanish or portuguese localizations.. and those are also amazingly easy and fast to get done. I don't know if it's AJAX.. but that makes pretty much every other web service I used seem as efficient as a bureaucratic government office on a banana republic.