Connect CDC (SQData) will detect out of sync conditions that have occurred due to issues outside of its control. The replication Engine by default is configured to compensate changes by converting updates to inserts (if the record does not exist in the target), inserts to updates (if the record already exists in the target) and to drop deletes (if the record does not exist in the target). The Engine can also be configured to do other things in response to these events, including termination of replication, exception processing or only exception reporting.
Beyond Compensation it is possible that under some situations an Engine may update newer data with older data. This is a corner case situation that may be required by some Source platform environments but one that can also be very useful when data has been re-capturing data from a point-in-time when the databases were known to be in a consistent state. SmartApply is a technique that utilizes an Connect CDC (SQData) managed time-stamp column that has been added to each Target table.