In the manner, time, or as agreed beforehand—i.e., as promised (commonly used adverbially).
約束通り、午後3時に来ました。
As promised, I came at 3 PM.
商品は約束通り明日発送されます。
The item will be shipped tomorrow as promised.
約束通りの対応に感謝します。
Thank you for handling it as promised.