Postgresql – Django in dock-compose can't see the database : Could not translate host name "db" to address: Name or service not known

I am currently on a project based around react in the frontend, django in the backend, postgresql for the database and nginx for the reverse proxy. Everything is linked up with a Docker-compose file.

Right now, I try to link my postgresql database to django.

However every time I try to launch my network with the docker-compose CLI, it fails with the migration of data in the django backend container with the following error:

#0 0.697 django.db.utils.OperationalError: could not translate host name "db" to address: Name or service not known

I do not understand why I have this error. When I try to check if the database is up, it works without any problem:

docker-compose up -d db     
Creating network "docker_nginx_django_react_template_appNetwork" with driver "bridge"
Creating db ... done
docker ps
CONTAINER ID   IMAGE             COMMAND                  CREATED         STATUS         PORTS                                       NAMES
_   postgres:latest   "docker-entrypoint.s…"   5 seconds ago   Up 4 seconds   0.0.0.0:5432->5432/tcp, :::5432->5432/tcp   db

Here is my docker-compose file :

version: '3.8'

services:
  nginx:
    container_name: app_server_conf
    build:
      context: ./
      dockerfile: ./Dockerfile
    ports:
      - "80:80"
    environment:
      - PUBLIC_URL=127.0.0.1
    volumes:
      - staticfiles:/staticfiles
    networks:
      - appNetwork
    depends_on:
      - backend    
  db:
    image: postgres:latest
    container_name: db
    restart: always
    ports:
      - "5432:5432"
    networks:
      - appNetwork
    environment:
      POSTGRES_HOST_AUTH_METHOD: trust
      POSTGRES_USER: test
      POSTGRES_PASSWORD: test
    volumes:
      - postgresql:/var/lib/postgresql/data
    healthcheck:
      test: pg_isready -U postgres

  backend:
    container_name: backend
    ports:
      - "8000:8000"
    build:
      context: backend
      dockerfile: ./Dockerfile
    command: "make run"
    networks:
      - appNetwork
    volumes:
      - staticfiles:/app/static/
    depends_on:
      db:
        condition: service_healthy
    links:
      - db:db

volumes:
  postgresql:
  staticfiles:

networks:
  appNetwork:
    driver: bridge

And here is my part of settings.py :

DATABASES = {
    'default': {
        'HOST':'db',
        "ENGINE": "django.db.backends.postgresql",
        'NAME': 'backend_db',
        'USER': 'test',
        'PASSWORD': 'test',
        'PORT': '5432',
    }
}

Unfortunately, after many researches on the internet, I am completely lost. What seems weird to me, is I can see the database in the network, like the result below. But even with a hard clean with docker system prune --force, it did nothing.

docker network inspect docker_nginx_django_react_template_appNetwork
[
    {
        "Name": "docker_nginx_django_react_template_appNetwork",
        ...,
        "Containers": {
            "cb7fdbfc4efe91254e95c02ca680315d488b0c6426ea90b2f682b74bf18eef62": {
                "Name": "db",
                "EndpointID": "endpointid",
                "MacAddress": "mac_address",
                "IPv4Address": "ip_address/20",
                "IPv6Address": ""
            }
        },
        ...
    }
]