Django Core Knowledge

Full Reference: See advanced.md for Django Channels setup, WebSocket consumers, JWT authentication middleware, broadcasting from views, room management, and WebSocket testing.

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: django for comprehensive documentation.

Model Definition

from django.db import models

class User(models.Model): name = models.CharField(max_length=100) email = models.EmailField(unique=True) created_at = models.DateTimeField(auto_now_add=True) is_active = models.BooleanField(default=True)

class Meta:
    ordering = ['-created_at']

def __str__(self):
    return self.name

Views (Class-Based)

from django.views.generic import ListView, DetailView, CreateView from django.urls import reverse_lazy

class UserListView(ListView): model = User template_name = 'users/list.html' context_object_name = 'users' paginate_by = 20

class UserDetailView(DetailView): model = User template_name = 'users/detail.html'

class UserCreateView(CreateView): model = User fields = ['name', 'email'] success_url = reverse_lazy('user-list')

Django REST Framework

from rest_framework import viewsets, serializers

class UserSerializer(serializers.ModelSerializer): class Meta: model = User fields = ['id', 'name', 'email', 'created_at']

class UserViewSet(viewsets.ModelViewSet): queryset = User.objects.all() serializer_class = UserSerializer

Key Commands

python manage.py makemigrations python manage.py migrate python manage.py createsuperuser python manage.py runserver

Project Structure

myproject/ ├── manage.py ├── myproject/ │ ├── settings.py │ ├── urls.py │ └── wsgi.py └── users/ ├── models.py ├── views.py ├── urls.py └── admin.py

When NOT to Use This Skill

• FastAPI projects - FastAPI is async-first with automatic OpenAPI docs

• Flask microservices - Django is heavyweight for simple APIs

• Non-Python backends - Use language-appropriate frameworks

• Real-time only apps - Consider Node.js or Go for WebSocket-heavy apps

• Serverless functions - Django startup time is too slow

Anti-Patterns

Anti-Pattern Why It's Bad Solution

N+1 queries Slow performance Use select_related() and prefetch_related()

No index on frequently queried fields Slow queries Add db_index=True to model fields

Using .filter() in loops Multiple DB hits Use .filter(id__in=list)

Storing sensitive data in settings.py Security risk Use environment variables

Missing CSRF protection XSS vulnerability Keep CsrfViewMiddleware enabled

Fat models Hard to test Move business logic to services

Quick Troubleshooting

Problem Diagnosis Fix

"No such table" error Migrations not applied Run python manage.py migrate

Static files not loading STATIC_URL misconfigured Run collectstatic in production

CSRF verification failed Missing CSRF token Add {% csrf_token %} to forms

"OperationalError: database is locked" SQLite concurrency Use PostgreSQL in production

Circular import errors Models importing each other Use get_model() or string references

Slow admin interface No list_select_related Add list_select_related to ModelAdmin

Production Readiness

Security Configuration

settings/production.py

DEBUG = False ALLOWED_HOSTS = env.list('ALLOWED_HOSTS') SECRET_KEY = env('SECRET_KEY')

Security headers

SECURE_SSL_REDIRECT = True SECURE_HSTS_SECONDS = 31536000 SECURE_HSTS_INCLUDE_SUBDOMAINS = True SECURE_CONTENT_TYPE_NOSNIFF = True X_FRAME_OPTIONS = 'DENY'

Session security

SESSION_COOKIE_SECURE = True SESSION_COOKIE_HTTPONLY = True CSRF_COOKIE_SECURE = True

Caching

CACHES = { 'default': { 'BACKEND': 'django.core.cache.backends.redis.RedisCache', 'LOCATION': env('REDIS_URL'), } }

Usage

from django.views.decorators.cache import cache_page

@cache_page(60 * 15) # 15 minutes def my_view(request): ...

Health Checks

from django.http import JsonResponse from django.db import connection

def health_check(request): return JsonResponse({'status': 'healthy'})

def ready_check(request): try: connection.ensure_connection() return JsonResponse({'status': 'ready', 'database': 'connected'}) except Exception as e: return JsonResponse({'status': 'not ready', 'error': str(e)}, status=503)

Gunicorn Configuration

gunicorn.conf.py

import multiprocessing

workers = multiprocessing.cpu_count() * 2 + 1 worker_class = 'uvicorn.workers.UvicornWorker' # For async bind = '0.0.0.0:8000' max_requests = 1000 timeout = 30

Testing

import pytest from django.test import Client

@pytest.fixture def authenticated_client(django_user_model): user = django_user_model.objects.create_user( username='test', password='test123' ) client = Client() client.force_login(user) return client

@pytest.mark.django_db class TestUserAPI: def test_create_user(self, api_client): response = api_client.post('/api/users/', { 'name': 'John', 'email': 'john@example.com' }, content_type='application/json') assert response.status_code == 201

Monitoring Metrics

Metric Target

Response time (p99) < 200ms

Error rate (5xx) < 0.1%

Database connections < pool size

Cache hit ratio

80%

Checklist

• DEBUG=False in production

• Security headers enabled

• HTTPS enforced (SSL redirect)

• Database connection pooling

• Redis caching configured

• Structured JSON logging

• Health/readiness endpoints

• Gunicorn with workers

• Static files on CDN

• pytest with fixtures

Reference Documentation

• Models & ORM

• Views Patterns