kubernetes – K8S HPA custom Stackdriver – 503 The service is currently not available – scaling is avoided

We have a Horizontal Pod Auto Scaler (HPA) Installed on gke clusterMost of the time the car scaler works perfectly. but from time to time (Especially during peak hours of our customers) The auto scaler is getting faster and faster Error code 503 from the stack driver,

Here are the mistakes we encounter:

Failed request to stackdriver api: googleapi: Error 503: The service is currently unavailable., backendError

and

"apiserver received an error that is not an metav1.Status: &googleapi.Error{Code:503, Message:"The service is currently unavailable.", Body:"{n  "error": {n    "code": 503,n    "message": "The service is currently unavailable.",n    "errors": (n      {n        "message": "The service is currently unavailable.",n        "domain": "global",n        "reason": "backendError"n      }n    ),n    "status": "UNAVAILABLE"n  }n}n", Header:http.Header(nil), Errors:()googleapi.ErrorItem{googleapi.ErrorItem{Reason:"backendError", Message:"The service is currently unavailable."}}}" 

Now I am a bit confused here; Google recommends using the Stackdriver as a source for HPAs (https://cloud.google.com/kubernetes-engine/docs/tutorials/external-metrics-autoscaling) if it is not 100% available or fault-tolerant – The cluster is just broken, because the pods are not enlarged and the resources are exhausted.

Does anyone know how to work here?

kubernetes – K8S – HPA without implementation object

I have played with k8s HPA – horizontal pod autoscaler. Things worked as expected (as explained here – https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale-walkthrough/)

When I delete the deployment kubectl delete deploy php-apache The deployment is deleted, pods are removed. However, the HPA record is still available for deployment. What is the meaning of this entry if there is no implementation object?