[{_id:"top1",countries:[{"id":"country_1","cities":[{"id":"city_1","areas":[{"id":"1"},{"id":"2"},{"id":"3"},{"id":"5"}]},{"id":"city_2","areas":[{"id":"1"},{"id":"2"},{"id":"3"},{"id":"4"}]}]}]}]

db.collection.aggregate([{"$addFields":{countries:{$map:{input:"$countries",in:{$map:{input:"$$this.cities",in:{"$mergeObjects":["$$this",{isDeliveringToArea:{$in:["5","$$this.areas.id"]}}]}}}}}}}])