A product search involves searching for the most relevant product from thousands or tens of thousands of products and presenting the most relevant products at the top of the list before other, less relevant, products. You can directly relate this problem to e-commerce websites, which sell huge numbers of products sold by many vendors or resellers.

Elasticsearch's full-text and relevance search capabilities can find the best-matching results. Presenting the best matches on the first page has great value as it increases the chances of the customer actually buying the product. Imagine a customer searching for the iPhone 7, and the results on the first page showing different cases, chargers, and accessories for previous iPhone versions. Text analysis capabilities backed by Lucene, and innovations added by Elasticsearch, ensure that the search shows iPhone 7 chargers and cases as the best match.

This problem, however, is not limited to e-commerce websites. Any application that needs to find the most relevant item from millions, or billions, of items, can use Elasticsearch to solve this problem.