When CloudWatch has insufficient data about the metric to determine the alarm state, the status that you want Amazon Route 53 to assign to the health check:
Healthy: Amazon Route 53 considers the health check to be healthy. Unhealthy: Amazon Route 53 considers the health check to be unhealthy. LastKnownStatus: Amazon Route 53uses the status of the health check from
the last time CloudWatch had sufficient data to determine the alarm state. For new health checks that have no last known status, the default status for the health check is healthy.