What is Kubernetes Pod Resource Requests vs Limits?

Question

Accepted Answer

**Requests** — guaranteed resources. **Limits** — maximum allowed resources.

```yaml
apiVersion: v1
kind: Pod
metadata:
  name: resource-pod
spec:
  containers:
  - name: app
    image: nginx:latest
    resources:
      requests:
        cpu: "250m"      # 0.25 CPU guaranteed
        memory: "128Mi"   # 128MB guaranteed
      limits:
        cpu: "1000m"     # 1 CPU maximum
        memory: "512Mi"  # 512MB maximum (OOM kill if exceeded)
---
# No limits (Burstable)
apiVersion: v1
kind: Pod
metadata:
  name: burstable-pod
spec:
  containers:
  - name: app
    image: nginx:latest
    resources:
      requests:
        cpu: "100m"
        memory: "64Mi"
      limits:
        cpu: "500m"
        memory: "256Mi"
---
# No requests/limits (BestEffort)
apiVersion: v1
kind: Pod
metadata:
  name: besteffort-pod
spec:
  containers:
  - name: app
    image: nginx:latest
    # No resources defined
```

```bash
# Check resource requests/limits
kubectl get pod resource-pod -o jsonpath='{.spec.containers[0].resources}' | jq

# Check actual usage
kubectl top pod resource-pod --containers
kubectl top pod resource-pod

# Check QoS class
kubectl get pod resource-pod -o jsonpath='{.status.qosClass}'

# Check node allocation
kubectl describe node node-1 | grep -A 5 "Allocated resources"

# Check LimitRange defaults
kubectl get limitrange -n default -o json | jq '.items[0].spec.limits'
```

**Behavior:**
- Requests: scheduling decision, guaranteed resources.
- Limits: enforced maximum (CPU throttled, memory OOM killed).

**CPU:**
- Requests: guaranteed CPU time.
- Limits: throttled if exceeded.

**Memory:**
- Requests: guaranteed memory.
- Limits: OOM killed if exceeded.

DevOps: What is Kubernetes Pod Resource Requests vs Limits?