The development of a search engine is a complex operation. The complexity depends on the features and type of service to be offered to users. To date, the company, but also the individual web developer, can build its own search engine using free tools. If the implementation of a general purpose search engine is objectively too costly in terms of resources, to develop a search engine optimized and customized for a specific segment is an opportunity to assess. http://www.devsapiens.com/en/post/1/build_your_own_search_engine_with_opensource_software_as_lucene_and_hadoop