Twitter has started indexing every public Tweet since 2006. So far, Twitter's search engine was surfacing breaking news and events in real time, but had an emphasis on recency. But from now on, people will be able to search through every Tweet ever published.

This new infrastructure enables many use cases, providing results for entire TV and sports seasons, conferences (#TEDGlobal), industry discussions (#MobilePayments), places, businesses and long-lived hashtag conversations across topics, such as #JapanEarthquake, #Election2012, #ScotlandDecides, #HongKong, #Ferguson and many more.

Twitter says its search service efficiently indexes roughly half a trillion documents and serves queries with an average latency of under 100ms.

For now, complete results from the full index will appear in the "All" tab of search results on the Twitter web client and Twitter for iOS & Twitter for Android apps. Over time, you’ll see more Tweets from this index appearing in the "Top" tab of search results and in new product experiences powered by this index.

Twitter has posted an interesting blog post online describing its new search service.