<p>Creates or updates one or more records and, optionally, creates a health check based on the settings in a specified service. When you submit a <code>RegisterInstance</code> request, the following occurs:</p> <ul> <li> <p>For each DNS record that you define in the service that's specified by <code>ServiceId</code>, a record is created or updated in the hosted zone that's associated with the corresponding namespace.</p> </li> <li> <p>If the service includes <code>HealthCheckConfig</code>, a health check is created based on the settings in the health check configuration.</p> </li> <li> <p>The health check, if any, is associated with each of the new or updated records.</p> </li> </ul> <important> <p>One <code>RegisterInstance</code> request must complete before you can submit another request and specify the same service ID and instance ID.</p> </important> <p>For more information, see <a href="https://docs.aws.amazon.com/cloud-map/latest/api/API_CreateService.html">CreateService</a>.</p> <p>When Cloud Map receives a DNS query for the specified DNS name, it returns the applicable value:</p> <ul> <li> <p> <b>If the health check is healthy</b>: returns all the records</p> </li> <li> <p> <b>If the health check is unhealthy</b>: returns the applicable value for the last healthy instance</p> </li> <li> <p> <b>If you didn't specify a health check configuration</b>: returns all the records</p> </li> </ul> <p>For the current quota on the number of instances that you can register using the same namespace and using the same service, see <a href="https://docs.aws.amazon.com/cloud-map/latest/dg/cloud-map-limits.html">Cloud Map quotas</a> in the <i>Cloud Map Developer Guide</i>.</p>

{
  "success": true,
  "data": {
    "id": "abc123",
    "created_at": "2025-01-01T00:00:00Z"
  }
}

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid request parameters"
  }
}