Mongo DB local -> oplog.$main collection keeps records of all changes which happen in the primary database, which are eventually read by secondaries to catch up data or syncup data in the mongo replica set.
A micro service can be written, which can pull up data / delta form oplog.$main based on the name space ( defined db and collection) and can save that data in destination Db or audit DB.
Later on audit DB can the queried to fetch the history or log data pertaining to entity.
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