cursor::begin() just calls into iterator::operator++() if the change stream has started [1], which means in change_stream_source_opeator.cpp code we could save a few places where we unnecessarily calls begin() or checking _it == _changeStreamCursor->end() [2]. Instead the logic could be simplified as

++_it;

if (_it != _changeStreamCursor->end())

{   \{process data}

} else

{   \{idle}

}

[1] https://github.com/mongodb/mongo-cxx-driver/blob/master/src/mongocxx/lib/mongocxx/v_noabi/mongocxx/change_stream.cpp#L46

[2]https://github.com/10gen/mongo/blob/master/src/mongo/db/modules/enterprise/src/streams/exec/change_stream_source_operator.cpp#L1135C9-L1135C22

https://github.com/10gen/mongo/blob/master/src/mongo/db/modules/enterprise/src/streams/exec/change_stream_source_operator.cpp#L1160