Database
[{_id:"1",ids:{user:"1"},time:400},{_id:"2",ids:{user:"1"},time:900},{_id:"3",ids:{user:"1"},time:950},{_id:"4",ids:{user:"2"},time:800}]
Query
db.collection.aggregate([{"$match":{time:{"$gt":700}}},{"$group":{"_id":"$ids.user","doc":{"$push":"$$ROOT"}}},{"$set":{"doc":{"$first":"$doc"}}},{"$replaceWith":"$doc"}])