Derived field and filter criteria in Atom Feeds

Summary:

We have a requirement to get real time changes only data out of Oracle cloud HCM. We are exploring atom feeds over HCM extracts to achieve this requirement as the information needs to be real time and on frequent basis. We have read through the documentation of atom feeds and are having the below questions which we feel wouldnt not be possble using atom feeds but would need confirmation.

1. Is there any way we can derive a custom field value based on different criteria using atom feeds and to fetch the changes only value of the field for the runs without using flexfields to derive and store this field value ? ( similar to using value sets and extract rule fast formula in case of extract).