Certification955 problems· 24 reviewed

CKA

955 incident response problems that help with CKA prep.

All problems (955)

K8S-1298A CronJob overlaps unexpectedlyA scheduled batch task starts producing duplicate side effects during node churn or maintenance windows.KubernetesIntermediate15 minProK8S-1282A DaemonSet never reaches the last nodeAn agent DaemonSet covers nearly the whole cluster and one newly introduced node group never picks it up.KubernetesIntermediate15 minProK8S-1290A Job runs successfully once and then flakesA batch process or long-running job reads a mounted secret once and later begins failing after an external rotation event.KubernetesIntermediate15 minProK8S-1316A mutating webhook seems available and pod creation still slows to a crawlA mutating webhook seems available and pod creation still slows to a crawl focuses on cluster-maintenance and asks the reader to isolate the key signal in Kubernetes. Fresh endpoints do not guarantee fresh dataplane state on every node.KubernetesIntermediate15 minProK8S-1296A node becomes Ready but DNS for hostNetwork pods failsA node image update appears safe and later hostNetwork workloads alone begin failing name resolution.KubernetesIntermediate15 minProK8S-1278A pod can reach services by IP but not by nameA monitoring or system pod using hostNetwork starts failing service discovery even though raw IP connectivity is fine.KubernetesIntermediate15 minProK8S-1286A readiness probe passes manually but fails in clusterA pod with a service-mesh or sidecar proxy starts answering locally and still fails readiness for the first minutes after launch.KubernetesIntermediate15 minProK8S-1311A StatefulSet rollout stalls only on replacement nodesA storage add-on update seems fine until stateful workloads land on new nodes and never attach volumes successfully.KubernetesIntermediate15 minProK8S-1292A validating webhook starts timing out only after a NetworkPolicy rolloutA security hardening rollout adds NetworkPolicies and later new workloads cannot be created due to webhook timeouts.KubernetesIntermediate15 minProK8S-1284An ALB ingress rule looks correct but one path returns 404A working ingress is migrated to a newer API version and only one nested route stops matching even though the rule appears equivalent.KubernetesIntermediate15 minProK8S-1276An ingress provisions but health checks stay redA service behind an ALB opens in the browser but keeps rotating targets in and out because health never goes green.KubernetesIntermediate15 minProK8S-1280A Service works inside the cluster but NLB traffic failsA LoadBalancer Service behaves perfectly in-cluster and starts failing only for outside clients after NLB source preservation enters the path.KubernetesIntermediate16 minProK8S-1268An ALB target group stays unhealthyA newly exposed service is reachable in a browser but the load balancer continues to mark every target unhealthy.KubernetesIntermediate16 minProK8S-1258An HPA stays at unknown metricsA team enables autoscaling and later discovers CPU or memory metrics never populate on an otherwise healthy deployment.KubernetesIntermediate16 minProK8S-1267Cluster autoscaler sees unschedulable pods but never scalesA cluster with pending workloads never scales up even though the autoscaler deployment itself appears healthy.KubernetesIntermediate16 minProK8S-1272CoreDNS runs but pods resolve external names incorrectlyAn EKS cluster starts returning odd external DNS results after a VPC-level network change, while CoreDNS remains Ready.KubernetesIntermediate16 minProK8S-094CronJob concurrency policy skips every runThe schedule is correct, but no new work starts because the previous Job remains non-terminal and blocks the concurrency guard forever.KubernetesAdvanced16 minProK8S-1274Metrics Server is installed but HPAs stay blindAn HPA remains at unknown metrics even after Metrics Server was installed and the pods appear healthy.KubernetesIntermediate16 minProK8S-119Mutating webhook injects a sidecar into completed Jobs and the cleanup controller loops on already-finished podsThe platform team adds injection globally, but batch workloads begin failing cleanup because completed pods no longer match the assumptions of the controller.KubernetesAdvanced16 minProK8S-387A controller update passes admission while the stored object still carries an old finalizer contract that the new controller no longer clears during a staged decommissionCreate and update succeed, but lifecycle completion is stuck behind a legacy finalizer path. The service still works through the primary path, but one dependency only fails when the old component is finally drained away.KubernetesAdvanced17 minPro