Kong load balance where upstream has different root paths?

I'm using Kong OSS (not container or k8s deployed) trying to load balance a backend two backend services for testing. My challenge is one requires authentication and different backend path port, whereas the other does not.

Frontend 1 - Kong API Gateway frontend

• Host: localhost
• Port: 8000
• Authentication: none
• Root Path: /
• Example Request: POST http://localhost:8000/ {JSON Data}

I'm expecting this front-end to have following backend

Backend A - local API service for testing

• Host: localhost
• Port: 80
• Authentication: none
• Root Path: /
• Example Request: POST http://localhost:80/ {JSON Data}

Backend B - hosted SaaS API service

• Host: s1.example.com
• Port: 443
• Authentication: API Key
• Root Path: /v7/guid/
• Example Request: POST https://s1.example.com/v7/guid/ {JSON Data}

Following the documentation, it seems I need to create 1 service to 2 upstream/targets, but not sure how to handle different upstream root paths?

Can the upstream config dynamically change the backend path based on selected upstream/target? Or maybe instead create a single route that load-balances between two services?

I'm trying to create 1 route with 1 service that has 2 upstream targets with different root paths and request-transformers for specific upstream targets

You can create two services, each service with one route. Both routes uses the same path,

Service 1: http://httpbin.org

curl --location --request POST 'http://localhost:8001/services/' \
--form 'name="httpbin"' \
--form 'url="http://httpbin.org"'

Route 1: /path

curl --location --request POST 'http://localhost:8001/services/httpbin/routes/' \
--form 'paths[]="/testPath"' \
--form 'name="httpbinget"' \
--form 'hosts[]="httpbin.org"'

Service 2: http://mockbin.org

curl --location --request POST 'http://localhost:8001/services/' \
--form 'name="mockbin-secure"' \
--form 'url="https://mockbin.org"'

Route 2: /testpath

curl --location --request POST 'http://localhost:8001/services/mockbin-secure/routes/' \
--form 'paths[]="/testPath"' \
--form 'name="mockbin-get"' \
--form 'hosts[]="mockbin.org"'

Test the API Gateway proxy /testPath

curl --location --request GET 'http://localhost:8000/testPath/' \
--header 'Accept: application/vnd.yang.data+json' \
--header 'Host: httpbin.org'

curl --location --request GET 'http://localhost:8000/testPath/' \
--header 'Accept: application/vnd.yang.data+json' \
--header 'Host: mockbin.org'

The 2nd request is expected to fail if it requires authentication, the last step will be to enable authentication plugin on this particular service

curl -X POST http://localhost:8001/services/mockbin-secure/plugins \
    --data "name=key-auth"  \
    --data "config.key_names=apikey" \
    --data "config.key_in_body=false" \
    --data "config.key_in_header=true" \
    --data "config.key_in_query=true" \
    --data "config.hide_credentials=false" \
    --data "config.run_on_preflight=true"

the apikey needs to be provided when testing the proxy

curl --location --request GET 'http://localhost:8000/testPath/' \
--header 'Accept: application/vnd.yang.data+json' \
--header 'Host: httpbin.org' \
--header 'api-key: somekey'

I don't have a secure service to test with now, I hope that might help.