Database
[{"_id":"657c54befca2b6a2cdd935ba","data":{"name":"Bob","surname":"xxx","age":"20"},"header":{"data":"1702646974156"},"_class":"Prova"},{"_id":"657c54befca2b6a2cdd935bb","data":{"name":"Tom","surname":"yyy","age":"25"},"header":{"data":"1702646974156"},"_class":"Prova"}]
Query
db.collection.aggregate([{$group:{_id:null,data:{$push:{"member":{"name":"$data.name","surname":"$data.surname"}}}}},{$project:{_id:0}}])