Hi Thomas,
Thanks for the suggestion on the synchronization method.
Regarding the SQL Server, it’s an on-premises instance ( SQL Server 2017) in our data center. We can connect to and operate our database in this instance fairly quickly via SQL Server Management Studio.
The workflow we adopted is basically as follows:
1. Build a database for our app on the SQL Server instance
2. Use ArcGIS for Desktop to run the Enable Enterprise Geodatabase tool to enable the database as an enterprise geodatabase
3. Set up relationship classes and indexes among the feature classes and tables
4. Drag the feature classes and tables over to a map within ArcMap or ArcGIS Pro
5. Publish them as a web layer (feature service) to the ArcGIS Online portal