What backend is compass, the search engine, using?
By default on Nuxeo 5.1 and Nuxeo 5.2 the compass backend is on the file system (with Hypersonic). With Nuxeo 5.2, Hypersonic has been replaced by Derby for every datasource, except for the compass backend, for which the switch to Derby has not been made possible yet (due to transaction problems). The file system backend for compass is the fastest and thus should not be changed unless for good reasons. Changing the default behavior is not straightforward. Be aware of it before going into this.