Sql agent or windows service? When is which needed?

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C#

SQL

I have a database db1 which has its own application developed with c#. There are several other applications, which each has its own database. These other applications store data in their own databases and record some documents in db1 using a stored procedure created in db1. The user of the db1 application needs to accept the document stored by the other application/database; when he accepts it, automatically some CRUD actions are performed in the database of the application that stored the document in db1. Db1 needs not to be aware of the other applications but the other way round because it is improper to modify db1 when new applications are developed in future. My question is how do I perform these CRUD actions automatically?: I was thinking of 1. Creating a job in mssql to perform that; when new applications are developed, a job is created for it to fetch the status of its document then perform the action in its database.
2. Creating windows service application for each of the applications, which periodically checks the status of the document it stored in db1, then perform the CRUD actions- this service will run on the server.
3. Creating a single windows service, which fetches the status of all documents, the perform CRUD actions on list of databases. When new applications are developed, their database is added to the list.

Any other suggestions are welcomed.

What I have tried:

I don’t know which option to choose: which is best