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In this article, we’ll compare Helm and Kustomize—two popular methods for managing Kubernetes manifests across different environments. Understanding their strengths, workflows, and trade-offs will help you select the best fit for your project.

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How Helm Works: Go-Templating in YAML

Helm uses Go templates to inject dynamic values into your Kubernetes manifests. Placeholders in the form of {{ .Values.variable }} are replaced at deploy time based on a values.yaml file. 
# templates/nginx-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Values.name }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Values.name }}
  template:
    metadata:
      labels:
        app: {{ .Values.name }}
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "nginx:{{ .Values.image.tag }}"

# values.yaml
replicaCount: 1
image:
  tag: "2.4.4"
name: "my-app"
When you run helm install my-app ./chart -f values.yaml, Helm merges the values into the templates, producing valid Kubernetes YAML: 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-chart
          image: "nginx:2.4.4"
Use --values (or -f) to specify different environment files, e.g., -f values.prod.yaml.

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Helm Chart Structure

A typical Helm chart directory might look like: 
k8s/
├── environments/
│   ├── values.dev.yaml
│   ├── values.stg.yaml
│   └── values.prod.yaml
└── templates/
    ├── nginx-deployment.yaml
    ├── nginx-service.yaml
    ├── db-deployment.yaml
    └── db-service.yaml
  • templates/: Kubernetes manifests with Go templating syntax.
  • environments/: Separate values.*.yaml files for each environment.

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Feature Comparison

FeatureHelmKustomize
Template SyntaxGo templates ({{ }})Pure YAML overlays and patches
Conditional Logic & Loops✔️ Supports if, range, custom functions❌ Not supported
Packaging & Versioning✔️ Full-fledged chart packaging, dependencies, hooks❌ No built-in packaging
Valid YAML Before Rendering❌ Not valid until helm template runs✔️ Always valid YAML
Native Kubernetes Integration✔️ Widely adopted, independent CLI✔️ Built into kubectl
Complex Helm charts with extensive logic can become hard to read and maintain. Ensure you document templates and values clearly.

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Trade-offs: When to Use Each Tool

  • Use Helm if
    • You need advanced templating (conditionals, loops, custom functions)
    • You want packaging, versioning, and chart dependencies
    • You require lifecycle hooks (e.g., pre-install, post-upgrade)
  • Use Kustomize if
    • You prefer pure YAML without an extra rendering step
    • You want easy-to-read overlays and patches
    • Your customization needs are straightforward (e.g., changing images, labels)
Balance your project’s complexity and team familiarity when choosing between the two.
The image is a slide comparing Kustomize and Helm, highlighting Helm's features such as being a package manager, providing conditionals, loops, functions, and hooks, and noting that Helm templates are not valid YAML due to Go templating syntax.

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References

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