Understanding Kubernetes Ingress and the Gateway API: Concepts, Comparison, and Best Practices

As Kubernetes becomes ubiquitous in cloud‑native environments, traffic management is essential; the platform offers Ingress and the emerging Gateway API to control external traffic entering a cluster.

Ingress provides a simple way to configure HTTP/HTTPS routing via a reverse proxy, allowing hosts to be mapped to services. Example manifest:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: name-virtual-host-ingress
spec:
  rules:
  - host: foo.bar.com
    http:
      paths:
      - pathType: Prefix
        path: "/"
        backend:
          service:
            name: service1
            port:
              number: 80
  - host: bar.foo.com
    http:
      paths:
      - pathType: Prefix
        path: "/"
        backend:
          service:
            name: service2
            port:
              number: 80

Despite its convenience, Ingress has critical drawbacks: limited to L7 HTTP(S) protocols, vendor‑specific controller implementations that cause lock‑in, and scalability issues for large clusters.

The Gateway API was introduced to address these limitations, offering a standardized, extensible traffic routing layer that supports multiple protocols (L4‑L7), reduces vendor dependence, and separates responsibilities through distinct resources.

GatewayClass describes the underlying gateway implementation (e.g., Nginx, Istio). Example:

apiVersion: gateway.networking.k8s.io/v1
kind: GatewayClass
metadata:
  labels:
    app.kubernetes.io/instance: nginx-gateway
    app.kubernetes.io/name: nginx-gateway
    app.kubernetes.io/version: 1.4.0
  name: nginx
spec:
  controllerName: gateway.nginx.org/nginx-gateway-controller

Gateway represents a concrete traffic entry point, referencing a GatewayClass and defining listeners (ports and protocols). Example:

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

Route resources (e.g., HTTPRoute, TCPRoute) define routing rules for different protocols. An HTTPRoute example that routes based on request headers:

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: foo-route
  labels:
    gateway: prod-web-gw
spec:
  hostnames:
  - foo.example.com
  rules:
  - backendRefs:
    - name: foo-v1
      port: 8080
  - matches:
    - headers:
      - name: traffic
        value: test
    backendRefs:
    - name: foo-v2
      port: 8080

The Gateway API also includes the GAMMA initiative (Gateway API for Mesh Management and Administration) to extend traffic management to east‑west (service‑to‑service) flows, aiming for a unified approach to both north‑south and east‑west traffic.

In summary, Ingress remains supported and is suitable for simple, small‑scale scenarios, while the Gateway API offers a more powerful, multi‑protocol, vendor‑agnostic solution for complex, large‑scale cloud‑native deployments.