Saving mongodb on volume using docker-compose

In my project I have few container managed by docker-compose. I would like to store data from mongoDB on persistent volume. MongoDB seems to store data in /data/db but files are not transferred to my host file system and they disappear after rebuilding container.

Here is my docker-compose config file:

version: '2'

services:

  db:
    image: mongo:latest
    volumes: 
      - "db-data:/data/db"
    ports:
      - "27017:27017"
    networks:
      - elk

  web: 
    build: ./app
    environment:
      - WAIT_COMMAND=1
    ports:
      - "3000:3000"
    networks:
      - elk
    depends_on: 
      - db


networks:
  elk:
    driver: bridge

volumes:
  db-data: