Kubernetes architecture, pods, deployments, and services

Kubernetes reconciles declared desired state. The control plane stores and schedules intent; nodes run Pods; Deployments manage replicated rollout; Services provide stable discovery across changing Pods.

At a glance

Question	Practical answer
When is it useful?	A Deployment requests three web replicas, the scheduler places Pods on nodes, and a Service selects healthy Pods by labels behind one stable name.
What should you do?	Deploy a stateless hello service locally, scale replicas, delete one Pod, and watch reconciliation replace it while the Service remains reachable.
How do you know it worked?	Desired and ready replica counts converge, labels select the intended Pods, rollout status completes, and deleting one Pod does not break the stable endpoint.
Common failure	A Pod is disposable; do not store irreplaceable state in its writable filesystem or depend on a Pod name staying constant.

flowchart LR
  A[Question] --> B[Kubernetes architecture, pods, deployments]
  B --> C[Small example]
  C --> D[Evidence]

The important idea is not to stop at a definition: connect the concept to a small example and observable evidence.

Worked example

A Deployment requests three web replicas, the scheduler places Pods on nodes, and a Service selects healthy Pods by labels behind one stable name.

Before acting, write the success signal. Change one condition at a time, observe the result, and record assumptions. For Kubernetes architecture, pods, deployments, and services, this separates what you know from what you are merely guessing.

Practice in 20–30 minutes

Goal: Deploy a stateless hello service locally, scale replicas, delete one Pod, and watch reconciliation replace it while the Service remains reachable.

1. Record the starting state and your prediction.
2. Implement the smallest version without adding unnecessary tools.
3. Change exactly one input or constraint and repeat.
4. Save a command, screenshot, output, or checklist as evidence.

Expected result: Desired and ready replica counts converge, labels select the intended Pods, rollout status completes, and deleting one Pod does not break the stable endpoint.

What can go wrong

A Pod is disposable; do not store irreplaceable state in its writable filesystem or depend on a Pod name staying constant.

When the result differs from your prediction, do not change many things at once. Check inputs, versions, environment, permissions, and logs, then repeat from the smallest example.

Definition of done

• I can explain the concept in my own words.
• I completed the small example and kept evidence.
• I know one failure mode and how to check it.
• Someone else can repeat the work without guessing missing steps.

Go deeper

Use the linked resource or repository at the end of the page when you need a full implementation. Check current versions before applying commands to a real project.