CircleCI 2.0 configuration for Ruby on Rails 5.1+ with headless chromedriver

circle.yml

# Ruby CircleCI 2.0 configuration file
#
# Check https://circleci.com/docs/2.0/language-ruby/ for more details
#
version: 2
jobs:
  build:
    docker:
      # specify the version you desire here
    - image: circleci/ruby:2.5.1-node-browsers
      environment:
      - PG_HOST=localhost
      - PG_PORT=5432
      - PG_PASSWORD=ubuntu
      - PG_USER=ubuntu
      - RAILS_ENV=test
      - RACK_ENV=test
    - image: postgres:9.6
      environment:
      - POSTGRES_USER=ubuntu
      - POSTGRES_DB=nowserving_test
    - image: bitjourney/elasticsearch-ci
    working_directory: ~/repo

    steps:
      - checkout

      # Download and cache dependencies
      - restore_cache:
          keys:
            - gem-cache-{{ checksum "Gemfile.lock" }}
            - gem-cache
            - gem-cache
      - run:
          name: Install Yarn
          command: |
            curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
            echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee -a /etc/apt/sources.list
            sudo apt-get --no-install-recommends install apt-transport-https
            curl -sL https://deb.nodesource.com/setup_9.x | sudo -E bash -
            sudo apt-get update
            sudo apt-get --no-install-recommends install nodejs yarn
            yarn --version
      - run:
          name: Install Latest Browsers
          command: |
            wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo apt-key add -
            sudo sh -c 'echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google-chrome.list'
            sudo apt-get update && sudo apt-get upgrade firefox
            sudo apt-get install google-chrome-stable
      - run:
          name: Install Ruby Dependencies
          command: gem install bundler && bundle install --jobs=4 --retry=3 --path vendor/bundle
      - save_cache:
          paths:
            - ./vendor/bundle
          key: gem-cache-{{ checksum "Gemfile.lock" }}
      - restore_cache:
          keys:
            - yarn-cache-{{ checksum "yarn.lock" }}
            - yarn-cache
            - yarn-cache
      - run: yarn install
      # Store yarn / webpacker cache
      - save_cache:
          key: yarn-cache-{{ checksum "yarn.lock" }}
          paths:
            - ~/.yarn-cache
      - run:
          name: Wait for DB
          command: dockerize -wait tcp://localhost:5432 -timeout 1m
      - run:
          name: Set up DB
          command: |
            bundle exec rake db:create db:schema:load --trace
      - run: bin/webpack
      # run tests!
      - run:
          name: run tests
          command: |
            mkdir /tmp/test-results
            TEST_FILES="$(circleci tests glob "spec/**/*_spec.rb" | circleci tests split --split-by=timings --timings-type=classname)"
            bundle exec rspec --format progress --format RspecJunitFormatter --out /tmp/test-results/rspec.xml --format progress $TEST_FILES
      # collect reports
      - store_test_results:
          path: /tmp/test-results
      - store_artifacts:
          path: /tmp/test-results
          destination: test-results

Why do you have multiple keys for the caches?