I am testing the performance of a hosted shortlist story map application (https://cosmos.surrey.ca/external/tools/avenuesofchange/assetmap/). The web map used for this shortlist story map was created using a tiled base map (UTM 10). I added a supporting layer that is part of a feature service that is hosted on ArcGIS online. https://services5.arcgis.com/YRpe0VKTJytZSSIB/arcgis/rest/services/EDI_CENSUS_TIME/FeatureServer/1
What I am finding using the developer tools on Chrome or Firefox is that multiple calls (over 20) are being made to https://services5.arcgis.com/YRpe0VKTJytZSSIB/arcgis/rest/services/EDI_CENSUS_TIME/FeatureServer/1 in order for the application to get the geometry of the layer to display on the map. The calls are only different in the extent of the image that it is trying to retrieve. The application seems to be trying to create the image in small tiles.
Normally a single call is sufficient to get the geometry.
The result of all of these calls is a very slow load of the application (> 10 seconds on desktop computer, far slower on mobile device).
Does anybody have an explanation of why multiple calls are being made?