diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
index eb474dc..462a418 100644
--- a/.github/workflows/checks.yml
+++ b/.github/workflows/checks.yml
@@ -16,6 +16,6 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
       - name: Test
-        run: docker-compose run --rm app sh -c "python manage.py test"
-      - name: Lint
+        run: docker-compose run --rm app sh -c "python manage.py wait_for_db && python manage.py test"
+      - name:
         run: docker-compose run --rm app sh -c "flake8"
\ No newline at end of file
diff --git a/Dockerfile b/Dockerfile
index 633552a..39f2150 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -12,11 +12,15 @@ EXPOSE 8000
 ARG DEV=false
 RUN python -m venv /py && \
     /py/bin/pip install --upgrade pip && \
+    apk add --update --no-cache postgresql-client && \
+    apk add --update --no-cache --virtual .tmp-build-deps \
+        build-base postgresql-dev musl-dev && \
     /py/bin/pip install -r /tmp/requirements.txt && \
     if [ $DEV = "true" ]; \
         then /py/bin/pip install -r /tmp/requirements.dev.txt ; \
     fi && \
     rm -rf /tmp && \
+    apk del .tmp-build-deps && \
     adduser \
         --disabled-password \
         --no-create-home \
diff --git a/app/app/calc.py b/app/app/calc.py
new file mode 100644
index 0000000..9b9849a
--- /dev/null
+++ b/app/app/calc.py
@@ -0,0 +1,12 @@
+"""
+Calculator functions
+"""
+
+
+def add(x, y):
+    """Add x and y and return result."""
+    return x + y
+
+
+def subtract(x, y):
+    return y - x
diff --git a/app/app/settings.py b/app/app/settings.py
index db01d07..787e479 100644
--- a/app/app/settings.py
+++ b/app/app/settings.py
@@ -10,6 +10,7 @@
 https://docs.djangoproject.com/en/3.2/ref/settings/
 """
 
+import os
 from pathlib import Path
 
 # Build paths inside the project like this: BASE_DIR / 'subdir'.
@@ -37,6 +38,7 @@
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.staticfiles',
+    'core',
 ]
 
 MIDDLEWARE = [
@@ -75,8 +77,11 @@
 
 DATABASES = {
     'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': BASE_DIR / 'db.sqlite3',
+        'ENGINE': 'django.db.backends.postgresql',
+        'HOST': os.environ.get('DB_HOST'),
+        'NAME': os.environ.get("DB_NAME"),
+        'USER': os.environ.get("DB_USER"),
+        'PASSWORD': os.environ.get('DB_PASS'),
     }
 }
 
diff --git a/app/app/tests.py b/app/app/tests.py
new file mode 100644
index 0000000..f81eb08
--- /dev/null
+++ b/app/app/tests.py
@@ -0,0 +1,22 @@
+"""
+Sample tests
+"""
+from django.test import SimpleTestCase
+
+from app import calc
+
+
+class CalcTests(SimpleTestCase):
+    """Test the calc module"""
+
+    def test_add_numbers(self):
+        """Test adding numbers together"""
+        res = calc.add(5, 6)
+
+        self.assertEqual(res, 11)
+
+    def test_substract_numbers(self):
+        """Test subtracting numbers"""
+        res = calc.subtract(10, 15)
+
+        self.assertEqual(res, 5)
diff --git a/app/core/__init__.py b/app/core/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/core/admin.py b/app/core/admin.py
new file mode 100644
index 0000000..6af52da
--- /dev/null
+++ b/app/core/admin.py
@@ -0,0 +1,3 @@
+from django.contrib import admin  # noqa
+
+# Register your models here.
diff --git a/app/core/apps.py b/app/core/apps.py
new file mode 100644
index 0000000..8115ae6
--- /dev/null
+++ b/app/core/apps.py
@@ -0,0 +1,6 @@
+from django.apps import AppConfig
+
+
+class CoreConfig(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
+    name = 'core'
diff --git a/app/core/management/__init__.py b/app/core/management/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/core/management/commands/__init__.py b/app/core/management/commands/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/core/management/commands/wait_for_db.py b/app/core/management/commands/wait_for_db.py
new file mode 100644
index 0000000..8230dbe
--- /dev/null
+++ b/app/core/management/commands/wait_for_db.py
@@ -0,0 +1,27 @@
+"""
+Django command to wait for the database to be available.
+"""
+import time
+
+from psycopg2 import OperationalError as Psycopg2Error
+
+from django.db.utils import OperationalError
+from django.core.management.base import BaseCommand
+
+
+class Command(BaseCommand):
+    """Django command to wait for database."""
+
+    def handle(self, *args, **options):
+        """Entrypoint for command"""
+        self.stdout.write("Waiting for database...")
+        db_up = False
+        while db_up is False:
+            try:
+                self.check(databases=['default'])
+                db_up = True
+            except (Psycopg2Error, OperationalError):
+                self.stdout.write('Database unavailable, waiting 1 second...')
+                time.sleep(1)
+
+        self.stdout.write(self.style.SUCCESS('Database available!'))
diff --git a/app/core/migrations/__init__.py b/app/core/migrations/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/core/models.py b/app/core/models.py
new file mode 100644
index 0000000..56b48a5
--- /dev/null
+++ b/app/core/models.py
@@ -0,0 +1,3 @@
+from django.db import models # noqa
+
+# Create your models here.
diff --git a/app/core/tests/__init__.py b/app/core/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/app/core/tests/test_commands.py b/app/core/tests/test_commands.py
new file mode 100644
index 0000000..46922ba
--- /dev/null
+++ b/app/core/tests/test_commands.py
@@ -0,0 +1,33 @@
+"""
+Test custom Django management commands.
+"""
+from unittest.mock import patch
+
+from psycopg2 import OperationalError as Psycopg2Error
+
+from django.core.management import call_command
+from django.db.utils import OperationalError
+from django.test import SimpleTestCase
+
+
+@patch('core.management.commands.wait_for_db.Command.check')
+class CommandsTestS(SimpleTestCase):
+    """Test commands."""
+
+    def test_wait_for_db_ready(self, patched_check):
+        """Test waiting for database if database ready"""
+        patched_check.return_value = True
+
+        call_command('wait_for_db')
+
+        patched_check.assert_called_once_with(databases=['default'])
+
+    @patch('time.sleep')
+    def test_wait_for_db_delay(self, patched_sleep, patched_check):
+        patched_check.side_effect = [Psycopg2Error] * 2 + \
+            [OperationalError] * 3 + [True]
+
+        call_command('wait_for_db')
+
+        self.assertEqual(patched_check.call_count, 6)
+        patched_check.assert_called_with(databases=['default'])
diff --git a/docker-compose.yml b/docker-compose.yml
index fbf9c6c..62c91e5 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -11,5 +11,28 @@ services:
     volumes:
       - ./app:/app
     command: >
-      sh -c "python manage.py runserver 0.0.0.0:8000"
-      
+      sh -c "python manage.py wait_for_db &&
+             python manage.py migrate &&
+             python manage.py runserver 0.0.0.0:8000"
+    environment:
+      - DB_HOST=db
+      - DB_NAME=devdb
+      - DB_USER=devuser
+      - DB_PASS=changeme
+    depends_on:
+      - db
+
+
+  db:
+    image: postgres:13-alpine
+    volumes:
+      - dev-db-data:/var/lib/postgresql/data
+    environment:
+      - POSTGRES_DB=devdb
+      - POSTGRES_USER=devuser
+      - POSTGRES_PASSWORD=changeme
+
+
+volumes:
+  dev-db-data:
+
diff --git a/requirements.txt b/requirements.txt
index 981b9a4..ef44a77 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,3 @@
 Django>=3.2.4,<3.3
-djangorestframework>=3.12.4,<3.13
\ No newline at end of file
+djangorestframework>=3.12.4,<3.13
+psycopg2>=2.8.6,<2.11
\ No newline at end of file