These performance issues could come from a variety of places. One simple thing I would do is just compare the execution times in the VDP admin tool of different queries to see whether certain data operations or sources seem to be slowing things down. I also might take a look at the execution trace in the VDP Admin tool to see if the queries are running as expected for example if the cache is being used when expected. Third party monitoring tools are also an option I might try for looking at the queries. In addition, I would look over the Performance Considerations section in the [Tableau and Denodo Best Practices](https://community.denodo.com/kb/en/view/document/Tableau%20and%20Denodo%20Best%20Practices?category=Northbound+Connections) article in the Denodo knowledge base. I would also look at the [Best Practices to Maximize Performance IV: Detecting Bottlenecks in a Query](https://community.denodo.com/kb/view/document/Best%20Practices%20to%20Maximize%20Performance%20IV:%20Detecting%20Bottlenecks%20in%20a%20Query?category=Best+Practices) article in the Denodo knowledge base. This article walks through how to go about detecting bottlenecks and how to solve them on the Denodo side of things. If you have a valid support user account, please open a new support case at support.denodo.com so that the support team can review the issue in detail.
Hope this helps!