I am learning Kubernetes. I have Apollo-express GraphQL API, React frontend and React Native app. How do I connect (or) what service type should I use if I want GraphQL API to be able to connect with both frontend and mobile apps?

I got a route /hi that replies Hi! to check if it's up:

app.get('/hi', function (_req, res) {
  res.send('Hi!')
})

Here's my attempt for api.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: server-api
spec:
  replicas: 2
  selector:
    matchLabels:
      app: server-api
  template:
    metadata:
      labels:
        app: server-api
    spec:
      terminationGracePeriodSeconds: 5
      containers:
        - name: server-api
          imagePullPolicy: IfNotPresent
          image: my/server-api:latest
          ports:
            - name: gql
              containerPort: 8081
          env:
            - name: NODE_ENV
              value: "development"
            - name: REDIS_HOST
              value: "redis-cache"
            - name: REDIS_PORT
              value: "6379"
            - name: POSTGRES_URL
              valueFrom:
                secretKeyRef:
                  name: postgres-url
                  key: POSTGRES_URL
---
apiVersion: v1
kind: Service
metadata:
  name: server-api
spec:
  type: ClusterIP
  selector:
    app: server-api
  ports:
  - name: gql
    port: 8081
    targetPort: 8081
---
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: server-api-external
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
    - http:
        paths:
          - path: /api
            backend:
              serviceName: server-api
              servicePort: 8081

Minikube IP is 192.168.99.100. But it shows Cannot GET / at 192.168.99.100/api/hi.

What I am doing wrong? Please help.