Kubernetes resources leveraged and illustrated by this blog article I wrote: Kubernetes Network Policies, how to secure the communications between your pods

To summarize, here are the bash commands you need to run:

# Get you AKS cluster with Calico enabled
az aks create... \
  --network-policy calico

# Since we would like to allow DNS resolution from WEB and API to respectively call API and DB we need to create a Label on the kube-system Namespace
kubectl label ns kube-system name=kube-system

# Create a Namespace to deploy K8S resources into it
ns=yournamespace
kubectl create ns $ns
kubectl config set-context \
  --current \
  --namespace $ns

# Deploy WEB, API and DB Pods/Services
kubectl apply \
  -f db-api-web-deployments.yaml

# Apply the first NetworkPolicy: deny all Ingress/Egress
kubectl apply \
  -f deny-all-netpol.yaml
 
# Apply the NetworkPolicy definition related to DB
kubectl apply \
  -f db-netpol.yaml

# Apply the NetworkPolicy definition related to API
kubectl apply \
  -f api-netpol.yaml

# Apply the NetworkPolicy definition related to WEB
kubectl apply \
  -f web-netpol.yaml