Zappos Uses Genetic Algorithms

Surprising application in place and an indication of multiple algorithms in parallel.

At Zappos, Algorithms Teach Themselves 
The Wall Street Journal  (with paywall)
Jared Council

Online shoe and clothing retailer Zappos sees promise in a self-learning algorithm's ability to address the problem of its search engine producing irrelevant results. Zappos' chief data scientist Ameen Kazerouni said several years ago his team began testing a genetic algorithm, which has since become critical to boosting the search engine's relevancy. Genetic algorithms generate various solutions to a problem, using natural-selection principles like reproduction and mutation to return the optimal or "fittest" solution. The algorithms were designed to parse out the intent of a search phrase, with those that perform best on an internal "relevance test," which models how users engage with search results, having the greatest odds of having their traits inherited by the next generation. Zappos uses three genetic algorithm engines in parallel to generate better search results.   .... "