I have deployed HPA to monitor the Memory and CPU, our application is not robust enough to handle the failures where it terminates the tasks when pod crashed or killed during scaledown, and needs manual intervention restart the tasks with dataloss and need lot of effort. I am looking around if there is a way to send a trigger a command send and receive before triggering a kill signal. I see prestop hook but not sure how exactly i can get this worked. Is it possible to trigger the prestop hook before sending the kill signal during scale down, where run a script in pod by monitoring and send back the signal to kubernetes when CPU or mem hits certain number and then kubernetes sends kill signal to initiate shutdown process. Any help/suggestions.?

NAME                                      REFERENCE                             TARGETS             MINPODS   MAXPODS   REPLICAS   AGE
horizontalpodautoscaler.autoscaling/hpa   Deployment/task-deployment1   545%/85%, 1%/75%            2         5         5          36h

below is the hpa manifest file

apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
metadata:
  name: hpa
  namespace: namespace-CapAm
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: task-deployment1
  minReplicas: 2
  maxReplicas: 5
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 75
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 85

We won't be able to use promotheus as it is not firm supported and we were suggested to use HPA with Mem and CPU only.