You can do it. When a user registers, you can ask him for certain information, in a selector place him to select the country and the profession. Then you save that in the database.
Then from another app, which can be the administrator, you do a reading of the database with a get database data, you just have to bear in mind that the Get can only filter for one field at a time, if you want double filters, it is To say that it brings you the users who live in Alazka and at the same time they are from the IT profession, you would have to save in your database a field where you have both data concatenated, for example a field called “CountryProfession”, and there you will save a concat to unite the country and the profession that the user selected when creating his account, that way, when doing the get, in the Order By you can put it to look for you in the “CountryProfession” field, the values that are equal to AlazkaTI (What would be the concatenated that you saved), that will bring you some records, and with one for each you can send notifications to all users who have that characteristic.
If you can manage it, but you already need knowledge in that area, to be able to generate a webhook in apphive, and to be able to send it to be executed externally.
And if you can move to another collection in the database, depending on the option you have chosen.