The author uses the terms API and "indexing technology" imprecisely here. I think what he really means is that they are getting data from Twitter via a push pr

The author uses the terms API and "indexing technology" imprecisely here. I think what he really means is that they are getting data from Twitter via a push protocol rather than a polling protocol. Note that while Twitter has a site-specific protocol (the firehouse), any site that wants to enable real time searching and alerts can also just implement PubSubHubbub, which can notify any interested subscriber about updates in near real time. As far as I know, Google uses PubSubHubbub to update Google Reader feeds in real time - I'm not sure if this integrates into realtime search results as of now.