The Global Earth Observation (GEO, 2005) was envisioned as a prelude to a Global Earth Observation System of Systems (GEOSS). The Common Infrastructure (GCI) is a geospatial cyberinfrastructure to facilitate the easy discovery, access, and utilization of Earth observation data, information, tools and services through standardized metadata (ISO 19139). The GEOSS Clearinghouse is the engine that drives the entire GCI. It provides a search capability against existing catalogues from GEO members and participating organizations, highlights the range of functionality possible, and creates a basis for a more persistent operational capability. The Center for Intelligent Spatial Computing at George Mason University (CISC) worked with the Federal Geographic Data Committee (FGDC) to research and develop such a clearinghouse and was later selected by GEO as the GEOSS clearinghouse. By Mar.3, 2011, 29 catalogs with 110 K metadata had been registered/harvested into the clearinghouse. A high performance based on Lucene and GeoTools search engine is integrated in the clearinghouse. All the metadata are converted into ISO 19139 and stored in the GEOSS clearinghouse database in the harvest process. Based on ISO 19139 template, text in each field can be easily parsed for text index with Lucene, and also spatial bounding box can be easily gotten for spatial index with GeoTools. With the integration of Lucene and GeoTools, both local and remote users can search against the hundreds of thousands of metadata to receive response in less than 2 second.