I’m using the woocommerce_thankyou hook in my WooCommerce site to send order data to an external URL via a POST request whenever a new order is created. However, I’ve noticed that this hook is sometimes triggering on very old orders, causing unexpected POST requests. Here’s the code I’m using:

add_action('woocommerce_thankyou', 'send_order_to_external_url', 10, 1);
    
    function send_order_to_external_url($order_id) {
        if (!$order_id) {
            return;
        }
    
        // Get the order details
        $order = wc_get_order($order_id);
    
        // Prepare the data to send
        $data = array(
            'order_id'      => $order_id,
            'order_total'   => $order->get_total(),
            'billing_email' => $order->get_billing_email(),
            'billing_phone' => $order->get_billing_phone(),
            // Add other necessary order details here
        );
    
        // Convert data to JSON
        $json_data = json_encode($data);
    
        // The endpoint URL
        $url = 'https://example.com/your-endpoint';
    
        // Send the data via wp_remote_post
        $response = wp_remote_post($url, array(
            'method'    => 'POST',
            'body'      => $json_data,
            'headers'   => array(
                'Content-Type' => 'application/json',
            ),
        ));
    
        // Check for errors (optional)
        if (is_wp_error($response)) {
            $error_message = $response->get_error_message();
            error_log('Error sending order data: ' . $error_message);
        }
    }

My questions are:

1. Why might the woocommerce_thankyou hook be triggering on old orders?
2. How can I prevent this hook from triggering on anything but newly created orders?

Any insights or suggestions to debug and fix this issue would be greatly appreciated!