Every field in every system should hold exactly the value a worker's current state calls for. You connect your systems and then describe how they should look when your worker has X state.
What does that mean? To give a few examples:
In Oracle Fusion, every worker assignment has a default expense account. Give Klef a table that maps each department or job code or anything to a default account. Klef can read that table and then update those assignments in Oracle so default expense account is always accurate.
A worker's name is in Slack, Gmail, etc. - each system has their own copy. You describe it once, as a property of the worker, and Klef writes it everywhere.
Move a worker from Sales to Logistics and downstream systems follow. The fields that depended on that worker belonging to the Sales department are recomputed for Logistics.
We treat your HRIS as the source of truth.