We had a customer who was having very slow render times for their feature service. After much testing we discovered that the layer used was created by importing a CSV file using "add XY data", exporting to file geodatabase then to enterprise geodatabase. The file geodatabase feature class was 8,000 characters in length and the Enterprise Geodatabase field length was a whopping 1,073,741,822 characters long! I tried setting the field length in excel but it didn't carry over into ArcGIS. If there is not a workaround anyone knows about, this is an FYI to Esri.
