Google does not need to pull up ALL results fast. It only needs to return 10 results quickly.
That's not relevant to the article, which says that the results are not available AT ALL. (Although as of my posting the two articles seem to be available again.)
True, but google is not searching there entire index for those. A simple linear search takes N time. So for a word that occurs billions of times. Google is not going to go through that entire list. They might use some clever hashing to jump around, and sorting. However, when trying to intersect two keywords they either have to pre-generate the intersection or make the data set they are intersecting small enough to get those 10 results quickly.
That's not relevant to the article, which says that the results are not available AT ALL. (Although as of my posting the two articles seem to be available again.)