Employing a declarative application deployment definition is the most effective approach. This method involves defining the desired state of all interdependent applications and their configurations in version-controlled manifests (e.g., YAML files, Helm charts, Kustomize overlays). This collection of manifests represents the entire application stack as a single, cohesive unit. GitOps tools, such as Argo CD or Flux, can then use this single source of truth to automatically and consistently reconcile the state across multiple Kubernetes clusters. This ensures that complex, interdependent applications are deployed and managed together in a reliable and scalable manner.

B. Creating separate Git repositories per application promotes isolation, which complicates the management of dependencies and the deployment of the applications as a single, unified group.

C. Direct deployments from a CI/CD pipeline represent an imperative (push-based) model, which is less robust for multi-cluster state management than a declarative (pull-based) GitOps model.

D. While Helm is a powerful packaging tool, relying on manual deployments is error-prone, does not scale, and undermines the consistency required for managing interdependent applications as a unit across clusters.

1. CNCF GitOps Working Group: The OpenGitOps Principles v1.0.0 states

"The desired state of a GitOps managed system must be: 1. Declarative". This principle is foundational for managing complex systems like multi-cluster applications as a single unit. (Source: OpenGitOps Principles

Section 2.1

Principle 1

available at https://opengitops.dev/)

2. Argo CD Documentation: The "App of Apps" pattern is a practical implementation of this declarative approach. An "app of apps" is a single declarative Argo CD Application resource that points to a Git repository containing the definitions for multiple

interdependent applications

managing them as a group. (Source: Argo CD - Declarative GitOps CD for Kubernetes

"App of Apps" pattern documentation).

3. Kubernetes Documentation: The official documentation emphasizes the benefits of declarative management. "When you use the declarative approach

you operate on Kubernetes objects by writing manifest files... Kubernetes itself will then ensure that the desired state you declared in your manifest is maintained." This principle extends to managing groups of applications. (Source: Kubernetes Documentation

Tasks > Manage Kubernetes Objects > Declarative Management of Kubernetes Objects Using Configuration Files).