Docker-compose: Load balance scaled up internal containers?

Hello!

I am checking out traefik with docker-compose and I cannot figure out how to use the LB for internal-only compose containers when they are scaled up. Mind you: this is just a test, if this is completely wrong please tell me.

What I want: There are 3 different services, one reachable from the outside (api) and scaled to 3 instances (which works fine), the others only reachable internally, with a HTTP call from the api container to the docker-compose hostname (also works fine). Now if I scale up the internal ones, there is (obviously) no LB to handle the round robin for these, as they don't have any entrypoints, and the call will always go to the first one. However if I add entrypoints these would also be available from the outside. What am I missing here?

This is the compose file:

version: "3.7"

services:
  traefik:
    image: "traefik:latest"
    command:
      - "--log.level=INFO"
      - "--api.insecure=true"
      - "--providers.docker=true"
      - "--providers.docker.exposedbydefault=false"
      - "--entrypoints.web.address=:80"
    ports:
      - "80:80"
      - "8080:8080"
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock:ro"
    depends_on:
      - api

  api:
    image: node:lts-alpine
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.api.rule=Host(`api.localhost`)"
      - "traefik.http.routers.api.entrypoints=web"
      - "traefik.http.middlewares.api.compress=true"
    working_dir: /app
    command: sh -c "npm i && npm run dev"
    env_file: ./.env
    depends_on: [jwt, auth]
    volumes:
      - ./api:/app
      - /app/node_modules
    expose:
      - 3000 # expose to traefik
    links:
      - auth
      - jwt
    scale: 3

  jwt:
    image: node:lts-alpine
    working_dir: /app
    volumes:
      - ./jwt:/app
      - /app/node_modules
    command: sh -c "npm i && npm run dev"
    env_file: ./.env

  auth:
    image: node:lts-alpine
    working_dir: /app
    volumes:
      - ./auth:/app
      - /app/node_modules
    command: sh -c "npm i && npm run dev"
    env_file: ./.env