{
  "id": "pod-affinity-mcq",
  "title": "Pod Affinity vs Anti-Affinity",
  "category": "Workloads & Scheduling",
  "difficulty": "Medium",
  "type": "mcq",
  "weight": 4,
  "description": "## Pod Affinity vs Anti-Affinity\n\nYou want to ensure that **cache** pods are always scheduled on the **same node** as the **app** pods they serve (to reduce latency). Which scheduling rule should you use in the cache pod spec?",
  "options": [
    {
      "id": "a",
      "text": "`spec.affinity.podAntiAffinity` with `requiredDuringSchedulingIgnoredDuringExecution` matching `app=app-pod`"
    },
    {
      "id": "b",
      "text": "`spec.affinity.podAffinity` with `requiredDuringSchedulingIgnoredDuringExecution` matching `app=app-pod`"
    },
    {
      "id": "c",
      "text": "`spec.affinity.nodeAffinity` with a `matchExpressions` for the app pod's node label"
    },
    {
      "id": "d",
      "text": "`spec.tolerations` with `key=app-pod` and `effect=NoSchedule`"
    }
  ],
  "correct_option": "b",
  "explanation": "**Pod Affinity** (`spec.affinity.podAffinity`) attracts pods to nodes where matching pods are already running. Use `requiredDuringSchedulingIgnoredDuringExecution` for a hard constraint (cache pod MUST co-locate with app pod) vs `preferredDuringSchedulingIgnoredDuringExecution` for a soft preference. **Pod Anti-Affinity** does the opposite — spreads pods apart. Tolerations are unrelated to co-location and work with taints.",
  "hints": [
    {
      "title": "Affinity types",
      "body": "podAffinity = attract to same node. podAntiAffinity = repel from same node. nodeAffinity = attract to nodes with specific labels. The `topologyKey: kubernetes.io/hostname` means 'same node'.",
      "command": "kubectl explain pod.spec.affinity.podAffinity"
    }
  ],
  "setup_commands": [],
  "default_namespace": "default",
  "teardown_commands": []
}