Kyverno vs OPA/Gatekeeper: Policy Engine Comparison

• 1. Architecture Comparison
• 2. Policy Language
  • Kyverno: YAML + CEL
  • OPA/Gatekeeper: Rego
• 3. Feature Comparison
• 4. Performance
• 5. Selection Guide
• 6. Summary

1. Architecture Comparison

Kyverno: Kubernetes-native, 3 controllers (Admission, Background, Reports), single CRD (ClusterPolicy), supports validate/mutate/generate/verifyImages.

OPA/Gatekeeper: General-purpose OPA + Kubernetes adapter, ConstraintTemplate + Constraint two-layer model, validation-focused with alpha mutation support.

2. Policy Language

Kyverno: YAML + CEL

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: require-labels
spec:
  rules:
    - name: check-app-label
      match:
        any:
          - resources:
              kinds: ['Deployment']
      validate:
        pattern:
          metadata:
            labels:
              app.kubernetes.io/name: '?*'

OPA/Gatekeeper: Rego

apiVersion: templates.gatekeeper.sh/v1
kind: ConstraintTemplate
metadata:
  name: k8srequiredlabels
spec:
  targets:
    - target: admission.k8s.gatekeeper.sh
      rego: |
        package k8srequiredlabels
        violation[{"msg": msg}] {
          provided := {l | input.review.object.metadata.labels[l]}
          required := {l | l := input.parameters.labels[_]}
          missing := required - provided
          count(missing) > 0
          msg := sprintf("Missing labels: %v", [missing])
        }

3. Feature Comparison

4. Performance

OPA/Gatekeeper compiles Rego policies for faster evaluation. Kyverno has YAML parsing overhead.

5. Selection Guide

Choose Kyverno when: Kubernetes-only, YAML-familiar team, need mutation/generation/image verification, minimize learning curve.

Choose OPA/Gatekeeper when: Use OPA outside Kubernetes, need complex policy logic, performance-critical at scale, team already knows Rego.

6. Summary

Both tools are production-proven. Choose based on team capabilities and requirements.