https://kubernetes.io/docs/concepts/workloads/controllers/deployment/

Declarative opertations description agaist a group of pods

2019
https://www.exoscale.com/syslog/kubernetes-zero-downtime-deployment/

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - image: quay.io/testing-farm/nignx:1.12
        name: nginx
        ports:
        - containerPort: 80
  ...