All of our production feature classes are in NAD 1983 Iowa State Plane North 2011 (wkid: 6463). We have a separate file gdb that we use for caching base maps where we load our production feature classes into this file gdb. The feature classes within our cache file gdb are in Web Mercator (wkid: 3857).
Below is a screenshot showing one of our parcel features overlaid on top of one of our base maps. You can see the parcel outline in gray within our base map. The pink parcel is the same feature as what is used to make the base map. The parcel service is in Iowa State Plane North spatial reference, while the base map is in Web Mercator spatial reference.
I'm wondering why the parcel service (pink) doesn't line up directly on top of the parcel outline in the base map? Am I missing something when publishing the service? Do I need to apply a transformation? Do I need to publish the service where the Data Frame is in Web Mercator as well?