Kubernetes: what is the difference between Deployment? What does it control?

Deployment in Kubernetes is an object that manages the creation and updating of a set of Pods. It is responsible for declaratively describing the desired state of the application: how many replicas should be running, which image version to use, the update strategy, etc.

Main functions of Deployment:

• Ensures the automatic launch of the required number of Pods.
• Allows smooth updating of the application (rolling update), minimizing downtime.
• Monitors the state of Pods and restores the required number in case of failures.

Example YAML Deployment:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: app-container
        image: my-app-image:v1

Thus, Deployment is an abstraction layer over ReplicaSet that simplifies managing the lifecycle of applications in Kubernetes.