What exactly do you have in dss_instance_api_url and API_KEY? The API node doesn't have a DSS API to access it so perhaps you are getting confused here. This URL should point to either a Designer or Automation node. And the API Key should be valid on those instances. While you can fetch a dataset from a Designer or Automation node from a API deployed in the API node you should consider if this is pattern you want to go for. API services can be deployed on High Available mode in Kubernetes. But if your API function has to fetch a dataset from a Designer or Automation node you will have a single point of failure there since neither Designer nor Automation node work in HA.