diff --git a/.circleci/config.yml b/.circleci/config.yml
index f5ff52b..8ca8a7e 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1,49 +1,51 @@
-version: 2.0
+version: 2.1
+
+commands: 
+    run-tests:
+        description: Install dependencies, load db and run tests
+        steps:
+          - checkout
+          - run: bundle install --path vendor/bundle
+          - run: bundle exec rake db:create db:schema:load
+          - run: rake
+
+executors:
+    docker-ruby:
+        parameters:
+            tag:
+                type: string
+        docker:
+            - image: circleci/ruby:<< parameters.tag >>
+            - image: circleci/postgres:9.4.12-alpine
+
+workflows:
+  ruby-test:
+    jobs: # run test suite concurrently on different versions of Ruby
+      - ruby-2-2
+      - ruby-2-3
+      - ruby-2-4
 
 jobs:
-  "ruby-2.2":
-    docker:
-      - image: circleci/ruby:2.2-node
-      - image: circleci/postgres:9.4.12-alpine
+  ruby-2-2:
+    executor: 
+        name: docker-ruby
+        tag: "2.2-node"
     working_directory: ~/circleci-demo-workflows
     steps:
-      - checkout
-      - run: bundle install --path vendor/bundle
-      - run: bundle exec rake db:create db:schema:load
-      - run:
-          name: Run tests
-          command: rake
+      - run-tests
 
-  "ruby-2.3":
-    docker:
-      - image: circleci/ruby:2.3-node
-      - image: circleci/postgres:9.4.12-alpine
+  ruby-2-3:
+    executor: 
+        name: docker-ruby
+        tag: "2.3-node"
     working_directory: ~/circleci-demo-workflows
     steps:
-      - checkout
-      - run: bundle install --path vendor/bundle
-      - run: bundle exec rake db:create db:schema:load
-      - run:
-          name: Run tests
-          command: rake
+      - run-tests
 
-  "ruby-2.4":
-    docker:
-      - image: circleci/ruby:2.4-node
-      - image: circleci/postgres:9.4.12-alpine
+  ruby-2-4:
+    executor: 
+        name: docker-ruby
+        tag: "2.4-node"
     working_directory: ~/circleci-demo-workflows
     steps:
-      - checkout
-      - run: bundle install --path vendor/bundle
-      - run: bundle exec rake db:create db:schema:load
-      - run:
-          name: Run tests
-          command: rake
-
-workflows:
-  version: 2
-  build:
-    jobs:
-      - "ruby-2.2"
-      - "ruby-2.3"
-      - "ruby-2.4"
+      - run-tests