Mongorestore allows for the number of concurrent insertion workers per collection to be increased using the [--numInsertionWorkersPerCollection](https://docs.mongodb.com/database-tools/mongorestore/#std-option-mongorestore.--numInsertionWorkersPerCollection) option. However, this is not available for mongomirror -- while you can increase the number of collections copied in parallel ([--numParallelCollections](https://docs.atlas.mongodb.com/reference/mongomirror/#std-option-mongomirror.--numParallelCollections)), there's no parameter surfaced to allow more inserts to be occurring at the same time over multiple threads within each collection. |t would be helpful to have a parameter like this to use to increase parallelization in order to increase the speed of migrations of large collections.