[{Category:"Phishing",response:1},{Category:"Security",response:1},{Category:"Privacy",response:1},{Category:"Privacy",response:1},{Category:"Privacy",response:0},{Category:"Mobile",response:1},{Category:"Mobile",response:1},{Category:"Desktop",response:1},{Category:"Desktop",response:0}]

db.collection.aggregate([{"$facet":{"top":[{"$group":{"_id":"$Category","response":{"$sum":"$response"}}},{"$sort":{"response":-1}},{"$limit":2}],"rest":[{"$group":{"_id":"$Category","response":{"$sum":"$response"}}},{"$sort":{"response":-1}},{"$skip":2},{"$group":{"_id":"Others","response":{"$sum":"$response"}}}]}},{"$project":{"data":{"$concatArrays":["$top","$rest"]}}},{"$unwind":"$data"},{"$replaceRoot":{"newRoot":"$data"}}])