In the PrepareConflictTracker, _prepareConflictStartTime is of type long long, but set equal to curTimeMicros64(), of type unsigned long long , in beginPrepareConflict().

The type of _prepareConflictStartTime's type should be consistent throughout prepare_conflict_tracker. Additionally, _prepareConflictDuration and _prepareConflictStartTime should be of the same type if possible.