Grafana queries to data source

I have a very basic query. Does Grafana issue the query to the data sources only when the dash boards are actively being visialized ?? Atleast from the packet capture I did, I see that the queries are issued only from the active dashboards/rows. Can you please confirm ? My system may have several dashboards with several panels for hundreds of devices in each dashboard. Just wanted to understand the scalability aspect of Grafana and hence the query.