[{id:1,name:"ram",age:25,group:"developer",salary:30000},{"id":2,"name":"sai","age":27,"group":"developer","salary":45000},{id:4,name:"ram",age:25,group:"developer",salary:300},{"id":12,"name":"sai","age":27,"group":"developer","salary":4100}]

db.collection.aggregate([{$sort:{"salary":-1},},{$limit:3}])