Skip to main content

Kubernetes Component Decision Tree

Hands-on example​

Goal: Choose the correct component combination using a decision tree.

Step 1: Workload lifetime​

Does the workload need to keep running?
│
├─ No
│   ├─ Runs once → Job
│   └─ Runs on a schedule → CronJob
│
└─ Yes → continue

Example (one-time task):

kubectl create job once --image=busybox -- sh -c 'echo done'

Step 2: Pod replaceability​

Can Pods be replaced freely?
│
├─ Yes → Deployment
│
└─ No
    ├─ Needs stable name
    ├─ Needs stable storage
    └─ Needs ordered startup/shutdown
        → StatefulSet

Example (stateless app):

kubectl create deployment api --image=nginx

Example (stateful app):

kubectl create statefulset db --image=nginx --service-name=db

Step 3: Self-healing requirement​

If a Pod dies, should Kubernetes recreate it?
│
├─ No → Pod
│
└─ Yes → keep Deployment / StatefulSet

Example (debug-only Pod):

kubectl run debug --image=busybox --restart=Never -- sh

Bad practice:

  • Do not use bare Pods for production
  • They are not self-healing

Step 4: Storage needs​

Does data need to survive Pod deletion?
│
├─ No → emptyDir
│
└─ Yes → PersistentVolumeClaim

Example:

kubectl create pvc data --storage=1Gi

Step 5: Network exposure​

Does anything need to talk to this workload?
│
├─ No → stop
│
└─ Yes
    ├─ Inside cluster only → Service (ClusterIP)
    └─ Outside cluster → continue

Example:

kubectl expose deployment api --port=80

Step 6: Traffic type​

Is traffic HTTP-based?
│
├─ No → Service (NodePort / LoadBalancer)
│
└─ Yes → Ingress + Service

Example:

kubectl apply -f - <<EOF
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: api
spec:
  rules:
  - host: api.local
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: api
            port:
              number: 80
EOF

Step 7: Configuration delivery​

Is the configuration sensitive?
│
├─ No → ConfigMap
│
└─ Yes → Secret
Does config need live updates?
│
├─ No → environment variables
│
└─ Yes → volume mount

Example:

kubectl create configmap cfg --from-literal=MODE=prod
kubectl create secret generic sec --from-literal=TOKEN=abc

Key observation​

  • Most applications resolve to: Deployment + Service
  • Add StatefulSet, Ingress, PVC, or Jobs only when the tree forces you
  • If you cannot justify a component with a question, you do not need it