[{"id":3,"parent_id":6,"translation":[{"language":"en","desc":"prod detail","name":"example1"},{"language":"tr","desc":"detaylar","name":"ornek1"}]}]

db.collection.aggregate([{$replaceRoot:{newRoot:{$mergeObjects:[{_id:"$_id",id:"$id",parent_id:"$parent_id"},{$arrayElemAt:[{$filter:{input:"$translation",cond:{"$eq":["$$this.language","en"]}}},0]}]}}}])