This project provides faceted search to the core Search module. It is an implementation of the Facet API, so display widgets and custom code can be reused by other modules that also integrate with Facet API.
Scalability is a known issue for SQL-based search, so do not expect this module (and core Search in general) to work well on larger sites. However, configuration and custom code can easily be ported after moving to more scalable solutions such as Apache Solr Search Integration or Acquia Search since both projects implement the Facet API.
Faceted Navigation for Search is maintained by Chris Pliakas.
Follow Chris on Twitter: @cpliakas