Django Interview Questions & Answers

 

Django Interview Questions & Answers — From Basics to Advanced

Preparing for a Django developer interview? Whether you’re aiming for a junior, mid-level, or senior backend role, mastering the key concepts and common questions will help you stand out.

In this article, we cover:

• Core Django concepts

• ORM and Models

• Views, Templates, and Forms

• REST APIs and Django REST Framework

• Performance & Deployment

1️⃣ What is Django and Why Use It?

Answer:
Django is a high-level Python web framework that enables rapid development of secure and maintainable web applications.

Key advantages:

• Follows MVC (MTV) architecture

• Includes ORM for database interaction

• Built-in authentication and admin interface

• Strong security features (XSS, CSRF, SQL injection protection)

• Rapid development with reusable apps

2️⃣ Difference Between @login_required and LoginRequiredMixin

Answer:

Feature	@login_required	LoginRequiredMixin
Usage	Function-Based Views	Class-Based Views
Placement	Decorator above the function	Inherits mixin in class                                                 definition
Example	@login_required def                 dashboard(request): ...	class           DashboardView(LoginRequiredMixin, TemplateView): ...

3️⃣ What is Django ORM? Difference Between select_related and prefetch_related

Answer:

• Django ORM allows interacting with the database using Python objects instead of SQL.

• select_related: Optimizes ForeignKey / OneToOne by joining tables in a single query.

• prefetch_related: Optimizes ManyToMany or reverse ForeignKey by fetching related objects in separate queries and joining in Python.

Example:

posts = Post.objects.select_related('author').prefetch_related('tags')

3️⃣ What is Django ORM? Difference Between select_related and prefetch_related
Answer:
Django ORM allows interacting with the database using Python objects instead of SQL.
select_related: Optimizes ForeignKey / OneToOne by joining tables in a single query.
prefetch_related: Optimizes ManyToMany or reverse ForeignKey by fetching related objects in separate queries and joining in Python.
Example:
posts = Post.objects.select_related('author').prefetch_related('tags')


5️⃣ Difference Between Function-Based Views and Class-Based Views
Answer:
Feature
                FBV
CBV
Structure
                Function
                  Class
Reusability        
                    Low
                  High
Scalability
                Limited
                  Excellent
Best Use
            Simple endpoints
             CRUD-heavy or large projects
6️⃣ How to Create a Custom User Model
Answer:
from django.contrib.auth.models import AbstractUser
from django.db import models

class CustomUser(AbstractUser):
    phone_number = models.CharField(max_length=15, blank=True)
Update settings.py:
AUTH_USER_MODEL = 'accounts.CustomUser'
Best practice: Always define custom user model at the start of the project.
7️⃣ What Are Django Signals?
Answer:

Signals allow decoupled event handling — trigger actions automatically when a model is saved, deleted, or updated.
Example:
from django.db.models.signals import post_save
from django.dispatch import receiver

@receiver(post_save, sender=CustomUser)
def create_profile(sender, instance, created, **kwargs):
    if created:
        Profile.objects.create(user=instance)

8️⃣ What is a ModelForm and Why Use It?
Answer:

A ModelForm is a form class that is directly tied to a Django model.
Automatically generates form fields from the model
Handles validation
Saves data to the database
Example:
class PostForm(forms.ModelForm):
    class Meta:
        model = Post
        fields = ['title', 'content']

9️⃣ How to Optimize Queries in Django?
Use select_related and prefetch_related
Limit fields with only() and defer()
Index frequently filtered columns
Avoid querying inside loops
Use caching (Redis / Memcached) for expensive queries

🔟 What is Django REST Framework (DRF)?
Answer:

DRF allows building RESTful APIs with Django.
Key features:
Serializers → Convert models to JSON and vice versa
ViewSets → Handle CRUD endpoints efficiently
Routers → Automatic URL routing
JWT / Token Authentication → Stateless, secure API

11️⃣ How to Handle Authentication & Permissions in DRF?
Use JWT or TokenAuthentication for API endpoints
Use IsAuthenticated, IsAdminUser, or custom permissions
Combine Groups and roles for fine-grained access control
Example:
from rest_framework.permissions import IsAuthenticated

class PostViewSet(ModelViewSet):
    permission_classes = [IsAuthenticated]

 Deployment Questions
Gunicorn → WSGI server for production
Nginx → Reverse proxy and static file handler
Docker → Containerization for reproducible environments
AWS EC2 / RDS / S3 → Production-ready infrastructure
Signals, Middleware, and Celery background tasks
Caching strategies (Redis / Memcached)
Query optimization and indexing
Asynchronous tasks and async views
Scaling strategies (horizontal vs vertical)