130+ Django Technical & Scenario Interview Questions with Answers

Preparing for technical interviews requires mastering both fundamental conceptual definitions and complex system design trade-offs. Below is an exhaustive repository of 130+ verified Django interview questions and expert answers, curated from top software companies, startups, and university placement rounds.

Track 1: Core Framework Architecture & MVT

Q1: What is the WSGI/ASGI specification and how does Django use it?
Answer: WSGI (Web Server Gateway Interface, PEP 3333) is the Python standard interface between web servers (like Nginx/Gunicorn) and web applications for synchronous traffic. ASGI (Asynchronous Server Gateway Interface) extends this standard to support asynchronous protocols, including WebSockets, HTTP/2, and long-polling connections. Django provides wsgi.py and asgi.py entry points to integrate with production application servers.

Q2: What is the execution order of Django middleware?
Answer: On the incoming request cycle, middleware executes in the top-to-bottom order declared in MIDDLEWARE inside settings.py. On the outgoing response cycle, execution reverses, executing from bottom-to-top. If any middleware returns an HttpResponse early during the request phase, the remaining chain and the view are bypassed.

Q3: How does Django implement the Singleton pattern?
Answer: Django uses singletons across several core modules, most notably in django.contrib.admin.site (a single shared instance of AdminSite) and in the application registry (django.apps.apps) which tracks all installed apps and models.

Track 2: Models, ORM & Database Tuning

Q14: What is select_for_update() and when is it required?
Answer: select_for_update() issues an SQL SELECT ... FOR UPDATE query, locking the matched database rows within an atomic transaction (with transaction.atomic():) until the transaction commits. This is essential for preventing concurrent financial deductions or double-booking in ticketing and banking applications.

Q18: What is the difference between Model.objects.filter(id=1).exists() vs if Model.objects.filter(id=1):?
Answer: .exists() generates an optimized SQL query: SELECT (1) AS "a" FROM "table" WHERE "id" = 1 LIMIT 1, returning a fast boolean without retrieving table columns. In contrast, if queryset: evaluates the entire QuerySet, loading full model instances and all column data into Python memory.

Track 3: Django REST Framework & Production Security

Q42: How do you prevent replay attacks with JWT tokens?
Answer: Replay attacks are mitigated by: 1) Keeping access tokens short-lived (15 minutes), 2) Enabling token rotation with SimpleJWT (ROTATE_REFRESH_TOKENS = True), 3) Blacklisting used refresh tokens in Redis or the database, and 4) Transmitting tokens exclusively over HTTPS with Strict-Transport-Security (HSTS).

Q55: How do you handle database connection pooling in high-traffic Django deployments?
Answer: By default, Django establishes a new database connection per thread and closes it at the end of the request. In high-traffic environments, opening and closing TCP sockets creates severe latency. Solutions include setting CONN_MAX_AGE = 60 in settings (reusing connections for 60 seconds) or placing an enterprise connection pooler like PgBouncer between Django and PostgreSQL.

Frequently Asked Questions (FAQ) - Student & Interview Review

Q1. How are the 130+ interview questions categorized in this guide?

The questions are organized into 7 targeted tracks: 1) Core Architecture & MVT, 2) Models, Migrations & ORM, 3) Views & Routing, 4) Forms & Validation, 5) Django REST Framework (DRF), 6) Performance, Caching & Celery, and 7) Security, Deployment & Architecture Scenarios.

Q2. What is the single most common question asked in Django interviews?

The most frequent question is: 'Explain the N+1 query problem, how do you identify it, and how do you resolve it using select_related vs prefetch_related?'

Q3. Are scenario-based architectural questions included?

Yes. Questions address real-world situations like handling high-traffic flash sales, preventing race conditions with F() expressions and select_for_update(), and architecting multi-tenant database schemas.

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