How does Stack Overflow display similar questions when you type in a new q​uestion?

This is one of the things that Stack Overflow and the rest of the sites that run on this platform do very well. As soon as you try to create a new ques开发者_运维技巧tion, a little window is shown that shows other similar questions. How is this done? What technology can be used to achieve this? Lucene, Sphinx, ...?

StackOverflow (and StackExchange in general) uses Lucene.net for full-text search.

Might want to read this as well.