使用支付网关API登录和交易密钥可以造成什么样的损害？

Currently, I'm in the process of hiring a web developer who will be working on a site that processes credit cards. While he won't have the credentials to log into the payment gateway's UI he will have access to the API login and transaction key since it's embedded in the application's code.Currently, I'm in the process of hiring a web d