Our client is a famous books reading community of Australia, with over 3,000,000 books available for search on website. The website was using mysql fulltext search to find matching books and authors. With growing database of books this search became slower and slower.
We implemented Sphinx Search to replace mysql fulltext search. The performance and accuracy of the search improved with this but its was not over yet. We further improved the results by incorporating more factors into ranking. We combined fulltext score with other factors like rating, number of readers etc. to better ranks books in search results.
This improved conversions from the search pages because users were able to find their desired books quickly.