Within one Dashboard

Within one dashboard, any panel that uses the exact same query settings (query, data source and timer) will result in only one query to the data source for all panels. For example if you add a line chart, bar chart and pie chart of the exact same query, the querying results are shared.

Note
Available in Enterprise edition.

Over All Dashboards and Users

In enterprise Pulse all polling queries to data sources are cached and results reused within the time intervals selected. This means whether there are 1, 10 or 100 users looking at the same dashboard with the same variables, it will only query once, NOT separately for every user.

This is obviously a dramatic improvement and massively reduces the load on the backend data source.

For example in the demo below there is a panel querying a small table with a 1 second interval. That panel has 8 instances open. With caching there is only 1 query per second. Without caching there are 8 queries per second. The same principle applies for panels open by different users.