I have an app that has hosted feature layer. I want to update the feature attribute fields with a 1 minute time interval from an external data source. i.e as data is coming in on an hourly basis into an external system, I want this data to automatically fill in the related fields in a feature attribute field.
#external data source
The easiest solution to this would be to use ArcGIS Server. Sounds like this is not an option, so you will need to script the changes from the external source to update the hosted feature service. What is the data type of the external source (i.e. CSV table, SQL Server)?
Can you place the CSV file on a web server? If you can, then you can add the CSV file as a web layer to your web map:
When the CSV file is updated on the web server, the changes will be reflected in the web map.