There is a polling interval in Options, which is defaulted to 5 seconds. The reason Sharptools is "fast" is it doesn't wait to confirm the change. Dashboard waits to confirm the change so you notice the polling interval.
Are you referring to the built-in Hubitat dashboard? As @patrick alluded to, the built-in Hubitat dashboards fall back to polling for status updates every few seconds when using the cloud links.
When using the built-in HE dashboards via the local links, your HE dashboard can access a websocket connection that runs on the hub which allows them to push event updates from the hub to your browser.
With SharpTools.io, all the events are pushed from your hub to SharpTools and down to your browser - acting a bit like a relay of sorts.
As @josh has pointed out, we don't implement any cloud storage or caching of your device data. Sharptools has a server that is receiving the data from the hub on every single event for subscribed devices. They then relay those changes to the dashboard.
With this said, Hubitat Dashboard will have a change to how commands are being sent coming up that will improve the perception of how long it takes to update.
Polling serves 2 purposes. 1) to get updates for things that changed in the background or outside of dashboard. ex. someone manually turns on a light.
and 2) to update and confirm a change has been made by a command sent from the dashboard.
Both these, prior to 2.0.9 used the same polling / check.
Coming up in 2.0.9 the command action, on/off, open/close, lock/unlock will have a separate short wait to see if the device updated and then fall back to the normal polling.