The Lucene/Solr search projectcurrently ranks among the top 15 open source projects and is one of the top 5 Apache projects, with installations at over 4,000 companies. Lucene/Solr downloads have grown nearly 10x over the past three years, with a current run-rate of over 6,000 downloads a day. The Solr search server, which provides application builders a ready-to-use search platform on top of the Lucene search library, was created by Yonik Seeley.

The search and discovery market is growing at 28% a year, with 2007 revenue of $1.8 billion. (IDC, Sept 2008). Apache Lucene/Solr offers an attractive alternative to the proprietary licensed search and discovery software vendors, owing to its:

• Best practice relevancy ranking
• Superior query performance (sub-second query speed and throughput)
• Proven scalability (e.g., running production search at Twitter, LinkedIn, Salesforce.com, Zappos, Wikipedia, Comcast Interactive Media, Apple, Technorati, Internet Archive, Netflix)
• Superior flexibility and customizability (well-written and easily modified)
• Low cost (open source)
• No vendor lock-in (open source)
• Low overhead and rapid incremental indexing
• Deep, broad query capabilities

The fact that Lucene/Solr are Apache open source software provides some significant advantages:

• Free to use -- no license fees whatsoever
• Complete source code, providing the independence and control one normally gets only by writing your own software. The Lucene/Solr Apache license allows users to produce or distribute derivative or proprietary works without restrictions.
• Code developed by programmers who are themselves end-users trying to solve pressing end-user needs
• Community -- A large, active and helpful community of developers and end-users, with forums and mailing lists for discussion and resolving problems and independent consultants offering more specialized assistance

Open source software -- Apache-licensed or otherwise -- also has some limitations as compared to the best commercial software:

• No formal support contracts
• No assured availability of training or other professional services to fulfill specific software needs or assist with building an application
• No formalized release testing program, release schedule or assurance of upgrade compatability, though Lucene/Solr contributions must have unit testing before they are committed to the code, and releases receive integrated testing