Get a record by external id

{
  "record": {
    "id": "1fba439a-208e-48e6-bd23-f6c97c3e0519",
    "externalId": "test-obj-1",
    "schemaId": "6449c3f3-b68d-46d1-850b-c8aea998ce1b",
    "fields": [
      {
        "id": "my-number-field",
        "value": 100
      }
    ],
    "relationships": {
      "primary-contact": [
        "14"
      ]
    },
    "createdTimestamp": "2021-04-16T16:12:22.222685095Z",
    "updatedTimestamp": "2021-04-16T16:13:12.022671090Z"
  }
}