Use daphne (ASGI) as the server

{{ cookiecutter.project_slug }}/Procfile

@@ -1,3 +1,3 @@
 release: ./manage.py migrate
-web: gunicorn --bind 0.0.0.0:$PORT {{ cookiecutter.pkg_name }}.wsgi
+web: daphne -b 0.0.0.0 -p $PORT {{ cookiecutter.pkg_name }}.asgi:application
 worker: REMAP_SIGTERM=SIGQUIT celery --app {{ cookiecutter.pkg_name }}.celery worker --loglevel INFO --without-heartbeat

{{ cookiecutter.project_slug }}/setup.py

@@ -37,6 +37,7 @@
     include_package_data=True,
     install_requires=[
         'celery',
+        'daphne',
         'django',
         'django-allauth',
         'django-configurations[database,email]',
@@ -48,7 +49,7 @@
         # Production-only
         'django-composed-configuration[prod]>=0.20',
         'django-s3-file-field[s3]',
-        'gunicorn',
+        'psycopg[pool]',
     ],
     extras_require={
         'dev': [

{{ cookiecutter.project_slug }}/{{ cookiecutter.pkg_name }}/settings.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import os
 from pathlib import Path
 
 from composed_configuration import (
@@ -10,19 +11,23 @@
     ProductionBaseConfiguration,
     TestingBaseConfiguration,
 )
+import dj_database_url
 
 
 class {{ cookiecutter.pkg_name.split('_')|map('capitalize')|join('') }}Mixin(ConfigMixin):
+    ASGI_APPLICATION = '{{ cookiecutter.pkg_name }}.asgi.application'
     WSGI_APPLICATION = '{{ cookiecutter.pkg_name }}.wsgi.application'
     ROOT_URLCONF = '{{ cookiecutter.pkg_name }}.urls'
 
     BASE_DIR = Path(__file__).resolve(strict=True).parent.parent
 
     @staticmethod
     def mutate_configuration(configuration: ComposedConfiguration) -> None:
-        # Install local apps first, to ensure any overridden resources are found first
         configuration.INSTALLED_APPS = [
+            # Install local apps first, to ensure any overridden resources are found first
             '{{ cookiecutter.pkg_name }}.{{ cookiecutter.first_app_name }}.apps.{{ cookiecutter.first_app_name.split('_')|map('capitalize')|join('') }}Config',
+            # Daphne must be listed before django.contrib.staticfiles in INSTALLED_APPS
+            'daphne',
         ] + configuration.INSTALLED_APPS
 
         # Install additional apps
@@ -46,4 +51,17 @@ class ProductionConfiguration({{ cookiecutter.pkg_name.split('_')|map('capitaliz
 
 
 class HerokuProductionConfiguration({{ cookiecutter.pkg_name.split('_')|map('capitalize')|join('') }}Mixin, HerokuProductionBaseConfiguration):
-    pass
+    @property
+    def DATABASES(self):  # noqa: N802
+        return {
+            'default': {
+                **dj_database_url.parse(os.environ['DATABASE_URL']),
+                'OPTIONS': {
+                    'pool': {
+                        # Adjust this pool size according to your postgres add-on service tier,
+                        # web dyno count, number of workers, etc.
+                        'max_size': 12,
+                    },
+                },
+            },
+        }