[{"_id":"5eff4376e036e45de9dbc6df","social_connections":{"friend":{"friends":[{"_id":"5eff42dee036e45de9dbc6d3","user_name":"x","name":"Viper King"},{"_id":"5eff40efe036e45de9dbc6c9","user_name":"z","name":"Brad Prasad Pitt"},{"_id":"5eff50337508da5ff40bf36e","user_name":"test","name":"Test"}]},"followers":{"following":[{"_id":"5eff42dee036e45de9dbc6d3","user_name":"x","name":"Viper King"},{"_id":"5eff40efe036e45de9dbc6c9","user_name":"z","name":"Brad Prasad Pitt"},{"_id":"5eff50337508da5ff40bf36e","user_name":"test","name":"Test"}]}}}]

db.collection.aggregate([{$project:{"social_connections.friend.friends":{$filter:{input:"$social_connections.friend.friends",as:"friend",cond:{$regexMatch:{input:"$$friend.name",regex:"Vi"}}}},"social_connections.followers.following":{$filter:{input:"$social_connections.followers.following",as:"follower",cond:{$regexMatch:{input:"$$follower.name",regex:"Vi"}}}}}}])