Database
[{"_id":ObjectId("60ddedd27e6b7be96409257b"),"user":ObjectId("60dded257e6b7be964092573"),"provider":"connectum","id":"62256402926432367","status":"new","amount":"94.00","currency":"US","extra":{"real_gift":ObjectId("60d1f2e580efe489fe150d75"),"user_id":245672982},"created_at":ISODate("2021-07-01T16:31:14.000Z")}]
Query
db.collection.aggregate([{"$group":{_id:"$user","my_field":{$sum:{"$toDouble":"$amount"}}}}])