From Publishers Weekly:

“Kadaxis, started by Chris Sim (formerly CTO of Bookish), uses data science to examine a book’s full text, customer reviews, and other related materials to formulate effective keywords to boost books’ discoverability in Amazon search. Its bookdiscovery.co website is a public-facing demonstration of the power of keywords in search. In July 2016, Kadaxis partnered with Firebrand to study the effectiveness of Sim’s approach, and the results for backlist titles in particular were impressive.”