Kubernetes Operator

End-to-end Kubernetes operator design and construction. Covers the operator pattern (control loops for stateful workloads), CRD design (schema, validation, conversion, status), the reconciliation loop (idempotency, convergence, level- vs edge-triggered), framework selection (controller-runtime / Kubebuilder / operator-SDK / metacontroller), and operational concerns (finalizers, leader election, RBAC scoping, status subresource, observability). Targets Go-based operators (the dominant ecosystem) with notes on alternatives (KOPF, JOSDK, kube-rs).

Core Capabilities

• Decide whether to write an operator — operator vs Helm vs GitOps vs admission webhook vs Crossplane, and when NOT to build one at all.
• CRD design — spec/status separation, OpenAPI v3 structural schemas, CEL cross-field validation, versioning, conversion webhooks, status subresource, printer columns, scale subresource.
• Reconciliation loops — idempotent, level-triggered, converging control loops; phase machines vs always-converge; owner references and garbage collection.
• Controller-runtime patterns (Go) — skeleton reconcilers, server-side apply, finalizers, leader election, watches/predicates/indexers, error classification, envtest.
• Framework selection — controller-runtime, Kubebuilder, operator-SDK, Metacontroller, KOPF, JOSDK, kube-rs.
• Operational hardening — finalizers, leader election, tightened RBAC, status conditions/observedGeneration, Prometheus metrics + structured logging.
• Anti-pattern audit — 24-entry catalog with severities, detection heuristics, and fixes for production-readiness review.

When to Use