Officially the helm charts are targeted to commercial users. As comparison to Standard or Enterprise, GraphDB Free allows for two "concurrent" reads and one "concurrent" write at any given time. However, the "concurrent" part depends on the semaphore being released and the release happens when the connection is closed. So, if you open one connection to execute a query on it and another connection to perform a size check - which, internally, would be another query - and do not close them, even sequential code will block. Calling the "connection.close()" method is required to reset the semaphore.