I am adding a Feature layer via ArcGIS Server. Using Snapshot mode takes 30 seconds to show the data and the OnDemand mode is unreliable in the results it displays, in that there are patches of data which are not displayed.
Currently the data set is quite small, with a only a few hundred features, and I've tried on Chrome/IE. etc..
I was able to produce the ondemand problem by doing the below:
If you change the zoom level to 5 and change the url to http://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer/3
,(3 instead of 2), you’ll notice that an area of the map does not display any counties around the Cincinnati area.
I'm using JS API 3.14 and ArcGIS Server 10.3