Deprecated features that are kept
What changes in Deprecated features that are kept compared with MongoDB and what your application has to do.
This difference is of the Deprecated and kept kind.
What MongoDB does
isMaster, collStats, mapReduce and the hedge preference are deprecated.
What TeselaDB does
They are kept with MongoDB's behaviour, because the drivers, mongosh and the tools still send them.
What your application has to do
For new code use their successors, which are hello, $collStats and the aggregation framework.