[{"_id":"ID_XXX","logs":[{"lead_id":123,"list_id":"list_44","order_id":"order_1"},{"lead_id":124,"list_id":"list_44","order_id":"order_2"}]},{"_id":"ID_YYY","logs":[{"lead_id":125,"list_id":"list_44","order_id":"order_2"},{"lead_id":126,"list_id":"list_44","order_id":"order_2"},{"lead_id":127,"list_id":"list_44","order_id":"order_3"},{"lead_id":128,"list_id":"list_66","order_id":"order_3"}]}]

db.collection.aggregate([{$unwind:"$logs"},{$group:{_id:"$_id",lists:{$push:"$logs.list_id"},orders:{$push:"$logs.order_id"}}}])