db={Users:[{_id:ObjectId("5e11d2d8ad9c4b6e05e55b82"),name:"vijay"},{_id:ObjectId("5ee5ca5fac47af698ab9f666"),name:"vijay1"}],Followers:[{_id:ObjectId("5ed0c8faac47af698ab9f659"),user_id:ObjectId("5e11d2d8ad9c4b6e05e55b82"),following:[ObjectId("5ee5ca5fac47af698ab9f666"),ObjectId("5df7c0a66243414ad2663088")],created_at:"2020-05-29T08:34:02.959+00:00"}]}

db.Followers.aggregate([{$match:{user_id:ObjectId("5e11d2d8ad9c4b6e05e55b82")}},{$project:{user_id:"$user_id",following:"$following"}},{$lookup:{from:"Users",let:{following:"$following"},pipeline:[{$match:{$expr:{$not:{$in:["$_id","$$following"]}}}}],as:"result"}}])