# Neptune Streams API Response Format
<a name="streams-using-api-reponse"></a>

A response to a Neptune Streams REST API request has the following fields:
+ `lastEventId`   –   Sequence identifier of the last change in the stream response. An event ID is composed of two fields: A `commitNum` identifies a transaction that changed the graph, and an `opNum` identifies a specific operation within that transaction. This is shown in the following example.

  ```
    "eventId": {
      "commitNum": 12,
      "opNum": 1
    }
  ```
+ `lastTrxTimestamp`   –   The time at which the commit for the transaction was requested, in milliseconds from the Unix epoch.
+ `format`   –   Serialization format for the change records being returned. The possible values are `PG_JSON` for Gremlin or openCypher change records, and `NQUADS` for SPARQL change records.
+ `records`   –   An array of serialized change-log stream records included in the response. Each record in the `records` array contains these fields:
  + `commitTimestamp`   –   The time at which the commit for the transaction was requested, in milliseconds from the Unix epoch.
  + `eventId`   –   The sequence identifier of the stream change record.
  + `data`   –   The serialized Gremlin, SPARQL, or OpenCypher change record. The serialization formats of each record are described in more detail in the next section, [Serialization Formats in Neptune Streams](streams-change-formats.md).
  + `op`   –   The operation that created the change.
  + `isLastOp`   –   Only present if this operation is the last one in its transaction. When present, it is set to `true`. Useful for ensuring that an entire transaction is consumed.
+ `totalRecords`   –   The total number of records in the response.

For example, the following response returns Gremlin change data, for a transaction that contains more than one operation:

```
{
  "lastEventId": {
    "commitNum": 12,
    "opNum": 1
  },
  "lastTrxTimestamp": 1560011610678,
  "format": "PG_JSON",
  "records": [
    {
      "commitTimestamp": 1560011610678,
      "eventId": {
        "commitNum": 1,
        "opNum": 1
      },
      "data": {
        "id": "d2b59bf8-0d0f-218b-f68b-2aa7b0b1904a",
        "type": "vl",
        "key": "label",
        "value": {
          "value": "vertex",
          "dataType": "String"
        }
      },
      "op": "ADD"
    }
  ],
  "totalRecords": 1
}
```

The following response returns SPARQL change data for the last operation in a transaction (the operation identified by `EventId(97, 1)` in transaction number 97).

```
{
  "lastEventId": {
    "commitNum": 97,
    "opNum": 1
  },
  "lastTrxTimestamp": 1561489355102,
  "format": "NQUADS",
  "records": [
    {
      "commitTimestamp": 1561489355102,
      "eventId": {
        "commitNum": 97,
        "opNum": 1
      },
      "data": {
        "stmt": "<https://test.com/s> <https://test.com/p> <https://test.com/o> .\n"
      },
      "op": "ADD",
      "isLastOp": true
    }
  ],
  "totalRecords": 1
}
```