With custom indexes, you can create new indexes for retrieving complex data to be used with the ContentStore API (CSAPI). You will find the CustomIndexes.cs file within the API Extensions Development Harness at [path-to-cms-site-instance]/App_Data/xml/Custom.
Important: Indexes are initialized during the Ingeniux CMS site startup. For any index changes, be sure to recycle the IIS application pool to apply changes.
For details and examples of indexes, see RavenDB's Static Indexes.