In this work, we consider metadata-based exploration of media collections using the M3 data model, to support multimedia analytics applications. We propose a new metadata-server implementation based on the Neo4j graph database system, and compare it to the existing, heavily-optimised server based on a relational database system. We show that the graph-based implementation performs well for interactive metadata-space retrieval, albeit not as well as the optimised relational implementation. The graph-based implementation also allows for very efficient updates to the metadata collection, however, which are practically impossible in the optimised relational implementation.