Things have changed a bit since 2009 :-) We rely heavily on Elasticsearch these days. The "related" questions now come from an Elasticsearch "More Like This" query.

Elastic uses tf-idf for most things, which is a standard search algorithm. Their particular implementation is documented here.

Things have changed a bit since 2009 :-) We rely heavily on Elasticsearch these days. The "related" questions now come from an Elasticsearch "More Like This" query.

Elastic uses tf-idf for most things, which is a standard search algorithm. Their particular implementation is documented here.

There are also some details in this blog post of 2010.