Код-ревью: оплата заказа

@Service
public class PaymentService {
    private final OrderRepository orders;
    private final PaymentGateway gateway;
    private final AuditRepository audit;
    private final MailSender mail;

    public PaymentService(OrderRepository orders, PaymentGateway gateway,
                          AuditRepository audit, MailSender mail) {
        this.orders = orders;
        this.gateway = gateway;
        this.audit = audit;
        this.mail = mail;
    }

    @Transactional
    public void pay(long orderId) throws PaymentException {
        Order order = orders.findById(orderId).orElseThrow();
        order.setStatus(Status.PAYING);
        GatewayResult r = gateway.charge(order.getTotal());
        if (!r.ok()) {
            writeAudit(orderId, "declined");
            throw new PaymentException("declined");
        }
        order.setStatus(Status.PAID);
        mail.send(order.getEmail(), "Оплачено");
    }

    @Transactional(propagation = Propagation.REQUIRES_NEW)
    public void writeAudit(long orderId, String text) {
        audit.save(new AuditRecord(orderId, text));
    }

    @Transactional
    private void refund(Order order) {
        gateway.refund(order.getTotal());
        order.setStatus(Status.REFUNDED);
    }
}