Cluster Model

A Kubernetes cluster is a group of machines that work together to run applications.

It is made of:

• Control Plane (brain)
• Worker Nodes (workers)
• Pods (applications)

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The Control Plane is the brain of Kubernetes.

It decides:

• Where applications run
• How many copies run
• What happens when something fails

Example:

• You say: “Run 3 replicas of my app”
• Control Plane ensures it happens

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Worker Nodes are machines that run your applications.

Example:

Node A → runs Pod 1, Pod 2 Node B → runs Pod 3

If a node fails:

• Kubernetes moves Pods to another node

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A Pod is the smallest unit in Kubernetes.

Example:

A Pod contains:

• Your application container (e.g. nginx)
• Optional helper containers

Example:

Pod = Web App Container

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User request flow:

User ↓ Service ↓ Pod ↓ Node

Control Plane ensures:

• Pods are created
• Pods are healthy
• Pods are distributed across nodes

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Think of a factory:

• Control Plane → factory manager
• Worker Nodes → machines
• Pods → products being produced