[{"_id":"1001","country":{"country_name":"India","capital_city":"Delhi","national_animal":"tiger","national_bird":"peacock","states":{"data":[{state_name:"karnataka",state_capital:"Bangalore"},{state_name:"maharashtra",state_capital:"Mumbai"},{state_name:"tamilnadu",state_capital:"Chennai"}]}},"country_name":"India","root_table":"country"}]

db.collection.aggregate([{$match:{"country.states.data.state_name":"maharashtra"}},{$project:{state:{$arrayElemAt:[{$filter:{input:"$country.states.data",cond:{$eq:["$$this.state_name","maharashtra"]}}},0]}}}])