Ontology-mediated query answering (OMQA) is a recent data management trend in the Artificial Intelligence, Database and Semantic Web areas, which aims at answering database queries on knowledge bases. Because it is an intricate combination of automated reasoning and database query evaluation, it raises major performance challenges. In this demonstration, we showcase a decade of OMQA optimization to understand "Where do we stand now and how did we get there?" and we highlight a promising new OMQA optimization that brings further significant performance improvement to discuss "What's next?".