How to fix 503 UC (Upstream Connection) in Kubernetes

kubectl describe <resource-type> <name> -n <namespace>
kubectl get events -n <namespace> --sort-by='.lastTimestamp'

kubectl get <resource-type> <name> -n <namespace> -o yaml
kubectl apply --dry-run=client -f resource.yaml

kubectl top nodes
kubectl top pods -A
kubectl describe nodes | grep -E "Allocated|Requests"

kubectl logs <pod-name> -n <namespace>
kubectl logs -n kube-system -l component=kubelet --tail=100

kubectl auth can-i <verb> <resource> --as=<user>
kubectl get rolebinding,clusterrolebinding -A | grep <resource>

kubectl get nodes
kubectl get apiservices
kubectl get ep kubernetes

kubectl explain <resource-type>
kubectl explain <resource-type>.spec

kubectl apply -f fixed-resource.yaml
kubectl rollout status <resource-type>/<name>