# Responses

For successful requests, the HTTP status code returned is 200. For failed requests, the HTTP status code returned is not 200, but 4xx or 5xx.

* 4xx: the parameters are illegal or the operation is not allowed.
* 5xx: the system error.

{% hint style="info" %} <mark style="color:blue;">**Note**</mark>

<mark style="color:blue;">Many Zenlayer Cloud APIs are asynchronous APIs. A successful request doesn't mean that the operation is completed and successful.</mark>
{% endhint %}

### Response for Successful Requests <a href="#response-for-successful-requests" id="response-for-successful-requests"></a>

For example, when calling bare metal API to create instances (CreateInstances), if the request has succeeded, you may see the response as shown below:

```
{
    "requestId": "T67723B59-F4D1-42EA-BDC1-5E67167FD8CC",
    "response": {
       "requestId": "T67723B59-F4D1-42EA-BDC1-5E67167FD8CC",
       "instanceIdSet" : ["1234567654321"],
       "orderNumber": "1234567654321"
    }
}
```

* **requestId:** the unique ID of an API request. Contact us with this ID when an exception occurs.
* **response:** as long as the API processes the request, it returns Response. does not matter if the request is successful or not.\
  Except for the fixed fields, all fields are action-specified. For the definitions of action-specified fields, see the corresponding API documentation.

### Response for Failed Requests <a href="#response-for-failed-requests" id="response-for-failed-requests"></a>

If the request has failed, you may see the response as shown below:

```json
{
    "requestId": "T67723B59-F4D1-42EA-BDC1-5E67167FD8CC",
    "code": "INVALID_ZONE_NOT_FOUND",
    "message": "The specified zoneId `SEL--A` is not found"
}
```

* **requestId:** the unique ID of an API request. Contact us with this ID when an exception occurs.
* **code:** the code of the error that helps you identify the cause and solution. You may find the code in either common error codes or API-specified error codes.
* **message:** the cause of the error. Note that the returned messages are subject to service updates. The information the messages provide may not be up-to-date and should not be the only source of reference.