🚀 Comprehensive Guide: How to Prepare for a Django Job Interview – 400 Most Common Interview Questions

Are you ready to get a job: https://hackmd.io/@husseinsheikho/django-mcq

#DjangoInterview #Python #WebDevelopment #Django #BackendDevelopment #RESTAPI #Database #Security #Scalability #DevOps #InterviewPrep

# Django ORM Comparison - Know both frameworks
# Django model (contrast with SQLAlchemy)
from django.db import models

class Department(models.Model):
    name = models.CharField(max_length=50)

class Employee(models.Model):
    name = models.CharField(max_length=100)
    email = models.EmailField(unique=True)
    department = models.ForeignKey(Department, on_delete=models.CASCADE)

# Django query (similar but different syntax)
Employee.objects.filter(department__name="HR").select_related('department')

# Async ORM - Modern Python requirement
# Requires SQLAlchemy 1.4+ and asyncpg
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession

async_engine = create_async_engine(
    "postgresql+asyncpg://user:pass@localhost/db",
    echo=True,
)
async_session = AsyncSession(async_engine)

async with async_session.begin():
    result = await async_session.execute(
        select(Employee).where(Employee.name == "Alice")
    )
    employee = result.scalar_one()

# Testing Strategies - Interview differentiator
from unittest import mock

# Mock database for unit tests
with mock.patch('sqlalchemy.create_engine') as mock_engine:
    mock_conn = mock.MagicMock()
    mock_engine.return_value.connect.return_value = mock_conn
    
    # Test your ORM-dependent code
    create_employee("Test", "test@company.com")
    mock_conn.execute.assert_called()

# Production Monitoring - Track slow queries
from sqlalchemy import event

@event.listens_for(engine, "before_cursor_execute")
def before_cursor(conn, cursor, statement, params, context, executemany):
    conn.info.setdefault('query_start_time', []).append(time.time())

@event.listens_for(engine, "after_cursor_execute")
def after_cursor(conn, cursor, statement, params, context, executemany):
    total = time.time() - conn.info['query_start_time'].pop(-1)
    if total > 0.1:  # Log slow queries
        print(f"SLOW QUERY ({total:.2f}s): {statement}")

# Interview Power Move: Implement caching layer
from functools import lru_cache

class CachedEmployeeRepository(EmployeeRepository):
    @lru_cache(maxsize=100)
    def get_by_id(self, employee_id):
        return super().get_by_id(employee_id)
    
    def invalidate_cache(self, employee_id):
        self.get_by_id.cache_clear()

# Reduces database hits by 70% in read-heavy applications

# Pro Tip: Schema versioning in CI/CD pipelines
# Sample .gitlab-ci.yml snippet
deploy_db:
  stage: deploy
  script:
    - alembic upgrade head
    - pytest tests/db_tests.py  # Verify schema compatibility
  only:
    - main

# Real-World Case Study: E-commerce inventory system
class Product(Base):
    __tablename__ = 'products'
    id = Column(Integer, primary_key=True)
    sku = Column(String(20), unique=True)
    stock = Column(Integer, default=0)
    
    # Atomic stock update (prevents race conditions)
    def decrement_stock(self, quantity, session):
        result = session.query(Product).filter(
            Product.id == self.id,
            Product.stock >= quantity
        ).update({"stock": Product.stock - quantity})
        if not result:
            raise ValueError("Insufficient stock")

# Usage during checkout
product.decrement_stock(2, session)

By: @DATASCIENCE4 🔒

#Python #ORM #SQLAlchemy #Django #Database #BackendDevelopment #CodingInterview #WebDevelopment #TechJobs #SystemDesign #SoftwareEngineering #DataEngineering #CareerGrowth #APIs #Microservices #DatabaseDesign #TechTips #DeveloperTools #Programming #CareerTips

• Fetch related ForeignKey objects in the same query.

entries = Entry.objects.select_related('author').all()

• Fetch related ManyToManyField objects in a separate efficient query.

entries = Entry.objects.prefetch_related('tags').all()

• Load only specific model fields.

entries = Entry.objects.only('headline')

• Defer loading of specific model fields.

entries = Entry.objects.defer('body_text')

• Execute raw, unmanaged SQL.

authors = Author.objects.raw('SELECT * FROM myapp_author')

• Get results as a list of tuples.

Entry.objects.values_list('headline', 'pub_date')

XV. Transactions

• Import the transaction module.

from django.db import transaction

• Run a block of code within a database transaction.

with transaction.atomic():
    # All database operations here are either committed together or rolled back.
    author.save()
    entry.save()

XVI. Managers & Model Methods

• Create a custom Manager for common queries.

class PublishedEntryManager(models.Manager):
    def get_queryset(self):
        return super().get_queryset().filter(status='published')

• Add a custom method to a QuerySet via its Manager.

Entry.objects.get_queryset().by_author("John Doe")

• Add a custom method to a model for object-specific logic.

class Entry(models.Model):
    #...
    def is_recent(self):
        return self.pub_date > timezone.now() - timedelta(days=1)

#Python #Django #ORM #Database #Backend

━━━━━━━━━━━━━━━
By: @DataScience4 ✨

✨ Quiz: How to Create a Django Project ✨

📖 Check your Django setup skills. Install safely and pin requirements, create a project and an app. Start building your first site.

🏷️ #basics #best-practices #django #web-dev

✨ How to Create a Django Project ✨

📖 Learn how to create a Django project and app in clear, guided steps. Use it as a reference for any future Django project and tutorial you'll work on.

🏷️ #basics #best-practices #django #web-dev

Build and Automate Django CRM

#Django #CRM #PYTHON

Build and Automate Django CRM

#Django #CRM #PYTHON

✨ Quiz: Getting Started With Django: Building a Portfolio App ✨

📖 Test your Django basics: frameworks, projects, views, templates, models, URLs, and migrations with practical questions.

🏷️ #basics #django #projects #web-dev