Hi,
I would create this application as a console application that can be run either directly using batch file or can be scheduled via Task Scheduler of windows.
I will retrieve the data from the external database using the APIs, will have to look into the API docs for that and populate the data in an Azure storage database for which the credentials will be configurable, so that you will only have to change the credentials in your configuration file and the Azure database will be connected automatically.
Regards,
Naveed Butt