75+ Kubernetes Operators Interview Questions and Answers [2025]

Core Kubernetes Operators Concepts

1. What is a Kubernetes Operator?

• Software extension for Kubernetes API.
• Manages apps via custom resources.
• Automates complex operational tasks.
• Uses reconciliation loops.
• Encodes human operator expertise.
• Handles stateful workloads.
• Extends Kubernetes functionality.

2. Why are Operators important for Kubernetes?

Operators automate the management of stateful applications, extending Kubernetes capabilities beyond native controllers to handle complex tasks like backups, scaling, and upgrades with custom logic.

3. When should you use an Operator?

• For stateful application management.
• When native controllers are insufficient.
• In multi-tenant environments.
• For automated backups or scaling.
• During failover or recovery.
• For application-specific upgrades.
• When codifying operational knowledge.

4. Where do Operators integrate in Kubernetes?

Operators run as custom controllers in the cluster, interacting with the API server to manage custom resources and reconcile cluster states.

They operate in dedicated namespaces or cluster-wide.

5. Who develops Kubernetes Operators?

• DevOps engineers for automation.
• SREs for reliability tasks.
• Platform teams for governance.
• Application owners for logic.
• Security specialists for compliance.
• Open-source contributors.
• Cloud provider teams.

6. Which components define an Operator?

An Operator includes Custom Resource Definitions (CRDs), a controller for reconciliation, and logic for tasks like backups or scaling.

7. How do Operators differ from native controllers?

• Operators use custom logic.
• Native controllers manage built-in resources.
• Operators leverage CRDs.
• Controllers use standard APIs.
• Operators handle stateful apps.
• Controllers focus on stateless.
• Operators automate complex ops.

Learn how policy-as-code complements Operators.

8. What is the Operator pattern?

• Codifies operational expertise.
• Uses control loops for reconciliation.
• Extends Kubernetes API.
• Automates app lifecycle tasks.
• Manages stateful services.
• Follows declarative principles.
• Minimizes manual intervention.

9. Why are CRDs critical for Operators?

CRDs extend the Kubernetes API, enabling Operators to define and manage custom resources with validation and defaulting for application-specific needs.

They ensure structured, declarative management.

10. When do Operators use control loops?

• To align desired and actual states.
• During resource provisioning.
• For continuous monitoring.
• In failure recovery scenarios.
• After configuration updates.
• During scaling operations.
• For version upgrades.

11. What role does reconciliation play in Operators?

• Compares desired vs. actual state.
• Triggers corrective actions.
• Ensures idempotent operations.
• Handles error conditions.
• Supports requeuing logic.
• Logs reconciliation events.
• Updates resource status.

12. Why use Operators for stateful applications?

Operators manage stateful apps by automating tasks like backups, failovers, and scaling, which require domain-specific knowledge beyond Kubernetes’ native capabilities.

13. When is an Operator preferred over Helm?

• For stateful app management.
• When needing custom logic.
• In complex operational tasks.
• For self-healing systems.
• During dynamic scaling.
• For failover automation.
• When Helm lacks flexibility.

14. Where do Operators store custom resources?

Custom resources are stored in the Kubernetes etcd, managed by the API server, and reconciled by Operators.

They persist like native resources.

15. Who benefits from using Operators?

• DevOps for automation.
• SREs for reliability.
• Platform teams for governance.
• Developers for app management.
• Security teams for compliance.
• Admins for cluster operations.
• End-users for simplicity.

16. Which Kubernetes APIs interact with Operators?

Operators interact with the Kubernetes API server, using CRDs and core APIs like Pods, Services, and ConfigMaps for resource management.

17. How do Operators handle upgrades?

• Manage CRD versioning.
• Support rolling updates.
• Handle data migrations.
• Test in staging.
• Monitor post-upgrade.
• Provide rollback plans.
• Automate upgrade tasks.

Explore CI/CD tools for Operator builds.

18. What is the purpose of finalizers in Operators?

• Prevent premature resource deletion.
• Ensure cleanup of dependencies.
• Support graceful shutdowns.
• Log cleanup actions.
• Handle external resources.
• Maintain data integrity.
• Enable safe uninstalls.

19. Why are Operators declarative?

Operators follow Kubernetes’ declarative model, defining desired states in CRs, allowing automated reconciliation without manual intervention.

This ensures consistency and scalability.

20. When do Operators need webhooks?

• For validating CR inputs.
• To set default configurations.
• During resource mutations.
• For admission control.
• In security-sensitive apps.
• For schema enforcement.
• Before production deployment.

Operator Development Frameworks

21. What is Operator SDK?

• Toolkit for Operator development.
• Supports Go, Helm, Ansible.
• Generates scaffolding code.
• Manages CRDs and RBAC.
• Integrates with OLM.
• Provides testing utilities.
• Simplifies deployment.

22. Why use Kubebuilder for Operator development?

Kubebuilder streamlines Go-based Operator creation with scaffolding, markers, and envtest for robust integration testing, aligning with Kubernetes SIG standards.

23. When should you choose Operator SDK?

• For Helm or Ansible Operators.
• When needing OLM integration.
• In multi-language projects.
• For rapid prototyping.
• With Operator Framework.
• For non-Go developers.
• When leveraging community tools.

24. Where does Kubebuilder provide advantages?

Kubebuilder excels in Go-centric projects, offering advanced webhook support and envtest for isolated testing.

It aligns with Kubernetes internals for precision.

25. Who maintains Operator SDK and Kubebuilder?

• Operator Framework for SDK.
• Kubernetes SIG for Kubebuilder.
• Red Hat for SDK contributions.
• CNCF community members.
• Go developers for code.
• Enterprise users for feedback.
• Open-source contributors.

26. Which framework is best for Ansible Operators?

Operator SDK supports Ansible-based Operators, enabling playbook-driven automation without requiring Go expertise.

27. How do Operator SDK and Kubebuilder differ?

• SDK supports multiple languages.
• Kubebuilder focuses on Go.
• SDK integrates with OLM.
• Kubebuilder excels in testing.
• SDK offers Helm support.
• Kubebuilder aligns with SIGs.
• Choice depends on project needs.

Discover service meshes for Operator-managed apps.

28. What is controller-runtime used for?

• Core library for controllers.
• Manages client interactions.
• Handles informers and caches.
• Supports reconciliation loops.
• Enables webhook servers.
• Provides scheme management.
• Used by SDK and Kubebuilder.

29. Why develop Helm-based Operators?

Helm-based Operators leverage chart templating, simplifying deployments for teams familiar with Helm, especially for stateless or simpler stateful apps.

They reduce coding overhead.

30. When is Kubebuilder ideal for production?

• For Go-based Operators.
• When needing precise control.
• In performance-critical setups.
• For advanced webhook needs.
• With complex testing requirements.
• For SIG-aligned projects.
• In Kubernetes contributions.

31. What are steps to build an Operator?

• Initialize with SDK/Kubebuilder.
• Define CRD for resources.
• Implement reconciler logic.
• Add RBAC permissions.
• Generate manifests and build.
• Test with envtest.
• Deploy to cluster.

32. Why scaffold APIs early in development?

Scaffolding APIs early defines the CRD structure, enabling validation and controller logic development with clear resource boundaries.

33. When implement validating webhooks?

• To enforce CRD schemas.
• During input validation.
• For security policies.
• In admission control.
• Before resource creation.
• For compliance checks.
• In production environments.

34. Where deploy Operators in clusters?

Operators deploy as Deployments in dedicated namespaces, watching cluster-wide or scoped resources via OLM or kubectl.

They integrate with cluster APIs.

35. Who defines Operator RBAC?

• Developers via markers.
• Admins for cluster roles.
• Security teams for audits.
• Platform owners for scopes.
• OLM for managed installs.
• SREs for permissions.
• Teams for reviews.

36. Which tools test Operators locally?

Envtest from controller-runtime provides an in-memory API server for isolated unit and integration testing of Operators.

37. How package Operators for distribution?

• Create OLM bundles.
• Define CSV manifests.
• Use semantic versioning.
• Include CRDs and RBAC.
• Sign for security.
• Publish to OperatorHub.
• Validate with scorecards.

38. What is the reconciler’s role?

• Implements control loop logic.
• Aligns desired and actual states.
• Handles error conditions.
• Triggers resource updates.
• Supports requeuing.
• Logs reconciliation events.
• Updates CR status.

Popular Operators in Kubernetes

39. What does the Prometheus Operator do?

• Manages Prometheus instances.
• Automates alerting rules.
• Handles ServiceMonitors.
• Supports cluster federation.
• Integrates with Grafana.
• Scales monitoring deployments.
• Manages config reloads.

40. Why use the Etcd Operator?

Etcd Operator automates highly available etcd clusters, managing backups, restores, and scaling for Kubernetes control plane reliability.

41. When deploy the Vault Operator?

• For dynamic secret management.
• In security-sensitive environments.
• During CI/CD integrations.
• For PKI certificate issuance.
• With audit logging needs.
• In multi-tenant clusters.
• For secure credential rotation.

42. Where does the Rook Operator apply?

Rook Operator provisions Ceph clusters for block, file, and object storage, simplifying software-defined storage in Kubernetes.

It automates storage lifecycle tasks.

43. Who uses the Jaeger Operator?

• Observability teams for tracing.
• Microservices architects.
• Performance engineers.
• DevOps for monitoring.
• SREs for debugging.
• Platform operators.
• Distributed system owners.

44. Which Operator manages databases?

Postgres Operator automates database clusters, handling high availability, backups, and failover for production workloads.

45. How does the Istio Operator work?

• Automates Istio control plane.
• Manages gateway configurations.
• Handles rolling upgrades.
• Supports canary releases.
• Monitors service health.
• Integrates sidecars.
• Scales mesh deployments.

Learn how incident response automation supports Operators.

46. What is the Cert-Manager Operator?

• Automates TLS certificates.
• Integrates with ACME providers.
• Manages secret resources.
• Handles certificate renewals.
• Supports validating webhooks.
• Secures ingress endpoints.
• Monitors expiration dates.

47. Why deploy the ArgoCD Operator?

ArgoCD Operator automates GitOps workflows, enabling declarative deployments and continuous synchronization for CI/CD pipelines.

It simplifies infrastructure automation.

48. When use the MySQL Operator?

• For stateful MySQL clusters.
• In high-availability setups.
• During backup automation.
• For scaling replicas.
• With monitoring integration.
• For database upgrades.
• In production environments.

Operator Best Practices

49. What are security best practices for Operators?

• Use least privilege RBAC.
• Run non-root containers.
• Validate webhook inputs.
• Sign OLM bundles.
• Audit API permissions.
• Apply PodSecurityPolicies.
• Monitor for anomalies.

50. Why test Operators before deployment?

Testing ensures reconciliation logic is correct, prevents production issues, and validates idempotency across various scenarios.

51. When version CRDs in Operators?

• For API stability.
• During schema changes.
• When adding fields.
• For deprecation plans.
• In release cycles.
• With migration strategies.
• For backward compatibility.

52. Where monitor Operator performance?

Monitor performance using Prometheus and Grafana, tracking reconciliation latency, error rates, and resource usage.

Integrate with cluster observability.

53. Who reviews Operator code?

• Developers for logic accuracy.
• Security teams for RBAC.
• SREs for reliability checks.
• Platform owners for integration.
• Open-source maintainers.
• Compliance auditors.
• End-users for usability.

54. Which practices ensure Operator idempotency?

Design reconcilers to produce consistent outcomes, avoiding side effects on repeated runs for reliable operations.

55. How handle Operator failures gracefully?

• Implement retry with backoff.
• Use leader election.
• Log detailed errors.
• Support graceful shutdowns.
• Add health probes.
• Update status fields.
• Integrate alerting.

56. What ensures clean Operator uninstalls?

• Use finalizers for cleanup.
• Remove managed resources.
• Handle dependency deletion.
• Preserve data if needed.
• Log uninstall actions.
• Support OLM cleanup.
• Ensure cluster hygiene.

Explore DORA metrics for Operator performance.

57. Why use OpenAPI schemas in CRDs?

OpenAPI schemas enforce validation, improve IDE support, and document CRD fields for better usability and error prevention.

They ensure robust configurations.

58. When scope Operators to namespaces?

• For tenant isolation.
• In multi-tenant clusters.
• To limit blast radius.
• For resource quotas.
• During development testing.
• For team boundaries.
• With namespace RBAC.

Advanced Operator Scenarios

59. What is leader election in Operators?

• Ensures single active reconciler.
• Uses lease resources.
• Handles failover scenarios.
• Supports high availability.
• Integrates with controllers.
• Monitors lease renewals.
• Logs election events.

60. Why integrate mutating webhooks?

Mutating webhooks modify resources at admission, setting defaults or enforcing configurations before persistence.

61. When use converting webhooks?

• For CRD version migrations.
• During storage conversions.
• For field transformations.
• In upgrade workflows.
• With multi-version APIs.
• For schema updates.
• To ensure compatibility.

62. Where expose Operator metrics?

Expose metrics via Prometheus for reconciliation duration, errors, and resource counts, integrating with cluster observability.

Enable dashboards for insights.

63. Who benefits from Operator Lifecycle Manager (OLM)?

• Admins for Operator installs.
• Developers for packaging.
• Users for catalog discovery.
• Teams for upgrades.
• Security for validation.
• Operators for distribution.
• Enterprises for lifecycle.

64. Which patterns handle Operator scaling?

Use leader election and distributed reconciliation to scale Operators in large clusters with high resource counts.

65. How manage Operator upgrades?

• Apply semantic versioning.
• Plan rolling updates.
• Migrate CRDs safely.
• Test in staging.
• Monitor post-upgrade.
• Provide rollback plans.
• Communicate changes.

66. What is scorecard testing for Operators?

• Validates Operator quality.
• Checks best practices.
• Assesses security compliance.
• Evaluates capability levels.
• Integrates with CI pipelines.
• Supports OLM submissions.
• Identifies improvement areas.

Operator Troubleshooting

67. What causes Operator reconciliation failures?

• Insufficient RBAC permissions.
• Invalid CR configurations.
• External service outages.
• Resource quota limits.
• Network connectivity issues.
• CRD version mismatches.
• Webhook validation errors.

68. Why use logs for Operator debugging?

Logs provide insights into reconciliation errors, state mismatches, and external dependencies, enabling root cause analysis.

69. When check CR status conditions?

• For resource readiness.
• During deployment checks.
• In troubleshooting workflows.
• For alerting triggers.
• With kubectl describe.
• For progress monitoring.
• In CI validation.

70. Where investigate webhook failures?

Check admission review logs and certificate validity when webhooks reject resources unexpectedly.

Use dry-run for testing.

71. Who resolves Operator RBAC issues?

• Admins for role bindings.
• Developers for RBAC markers.
• Security teams for audits.
• SREs for troubleshooting.
• Platform owners for scopes.
• Teams for permission reviews.
• Tools for validation.

72. Which tools assist Operator debugging?

Kubectl, k9s, and controller-runtime logging help inspect events, CR states, and reconciliation errors.

73. How address stale cache issues?

• Force resync intervals.
• Clear informer caches.
• Monitor enqueue rates.
• Use event handlers.
• Test in fresh clusters.
• Adjust concurrency settings.
• Log cache hits.

Learn how multi-cloud deployments impact Operators.

74. What indicates leader election issues?

• Multiple active reconcilers.
• Lease acquisition failures.
• High CPU contention.
• Stale reconciliation loops.
• Failover delays.
• Lease event logs.
• Pod restarts.

75. Why monitor Operator resource usage?

Monitoring CPU and memory usage identifies inefficient reconcilers or leaks, ensuring cluster stability.

Alerts prevent performance degradation.

76. When restart Operator deployments?

• After config updates.
• For cache corruption.
• During memory leaks.
• In failover testing.
• Post-upgrade validation.
• When logs show errors.
• For graceful restarts.