What is Kubernetes Gateway API?

The Gateway API is a set of CRDs (Custom Resource Definitions) that define how traffic enters your cluster.

Managed by: Kubernetes SIG Network
Designed as a replacement for: Ingress

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Key Components

1. GatewayClass

• Defines the type of gateway implementation
• Managed by platform teams

Example:

apiVersion: gateway.networking.k8s.io/v1
kind: GatewayClass
metadata:
  name: nginx
spec:
  controllerName: k8s.io/nginx-gateway-controller

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2. Gateway

• Represents the actual load balancer
• Defines listeners (HTTP, HTTPS, TCP)

Example:

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: my-gateway
spec:
  gatewayClassName: nginx
  listeners:
  - name: http
    protocol: HTTP
    port: 80

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3. HTTPRoute

• Defines routing rules
• Similar to Ingress rules but more powerful

Example:

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: my-route
spec:
  parentRefs:
  - name: my-gateway
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /app
    backendRefs:
    - name: my-service
      port: 80

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🧠 Why Gateway API (vs Ingress)?

Feature	Ingress	Gateway API
Flexibility	Limited	High
Role separation	NO	(Dev vs Platform team)
Traffic splitting	Basic	Advanced
Protocol support	Mostly HTTP	HTTP, TCP, gRPC
Extensibility	Low	High

Flow:

1. User → Load Balancer (Gateway)
2. Gateway → Listener (port/protocol)
3. Listener → HTTPRoute
4. HTTPRoute → Kubernetes Service
5. Service → Pods

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How to Implement Gateway API (Step-by-Step)

Step 1: Install Gateway API CRDs

kubectl apply -f https://github.com/kubernetes-sigs/gateway-api/releases/latest/download/standard-install.yaml

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Step 2: Install Gateway Controller

You need a controller like:

• NGINX Gateway Controller
• Istio
• Traefik

👉 Example (NGINX):

helm install nginx-gateway oci://ghcr.io/nginxinc/charts/nginx-gateway-fabric

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Step 3: Create GatewayClass

apiVersion: gateway.networking.k8s.io/v1
kind: GatewayClass
metadata:
  name: nginx
spec:
  controllerName: k8s.io/nginx-gateway-controller

---

Step 4: Create Gateway

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: app-gateway
spec:
  gatewayClassName: nginx
  listeners:
  - name: http
    protocol: HTTP
    port: 80

---

Step 5: Deploy Application

apiVersion: v1
kind: Service
metadata:
  name: app-service
spec:
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 8080

---

Step 6: Create HTTPRoute

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: app-route
spec:
  parentRefs:
  - name: app-gateway
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /
    backendRefs:
    - name: app-service
      port: 80

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Step 7: Verify

kubectl get gateway
kubectl get httproute
kubectl describe gateway app-gateway

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Real-Time Use Cases (Important for Interviews)

1. Microservices Routing

• /user → user-service
• /order → order-service

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2. Canary Deployment

• 90% → v1
• 10% → v2

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3. Multi-Tenant Clusters

• Platform team manages Gateway
• Dev team manages Routes

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4. API Gateway Replacement

• Works like AWS API Gateway inside cluster

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Pro Tips (Architect Level)

• Use Gateway API + EKS + AWS Load Balancer Controller
• Combine with Service Mesh (Istio) for advanced routing
• Use TLS termination at Gateway
• Integrate with WAF + security policies

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When to Use Gateway API?

Use Gateway API when:

• You need advanced routing (canary, A/B testing)
• You want separation of concerns
• You are building enterprise-grade Kubernetes platform

Avoid when:

• Simple apps → Use Ingress