load balancing AWS

If you are preparing for Python/Django backend interviews, then you’ll not only face questions on Django itself but also on SQL, APIs, caching, and cloud (AWS). Therefore, in this blog, I’ve compiled some of the most frequently asked questions along with clear and concise answers. However, these examples will help you understand the concepts better and prepare more effectively for your next interview. My advice is to prepare more questions in SQL because, for Django developers, it is often difficult to learn SQL due to relying heavily on the ORM. Therefore, practicing SQL separately will strengthen your backend fundamentals and give you more confidence in interviews. 1. What is the Longest Substring Problem? The longest substring problem usually refers to finding the longest substring without repeating characters. def longest_substring(s): seen = set() left = 0 start = 0 max_len = 0 for right in range(len(s)): while s[right] in seen: # shrink window if duplicate found seen.remove(s[left]) left += 1 seen.add(s[right]) if (right – left + 1) > max_len: max_len = right – left + 1 start = left # track start index of longest substring return s[start:start + max_len] # Example print(longest_substring(“abcabcbb”)) # Output: “abc” 2. What are the Types of Indexing in Databases? A database technique that speeds up query performance by creating data pointers: 3. How Do I Write the Longest SQL Query? This is a trick question — instead of “long queries,” interviewers expect optimized queries. 4. How Do You Make Fast APIs in Django Rest Framework (DRF)? Ways to optimize DRF APIs: 5. Can an Anonymous User Store Cart Items? An anonymous user’s cart items can be stored using sessions or cookies. The cart data (like product IDs and quantities) is kept in the session or browser storage until the user logs in. Once they log in, the session/cart data is merged into the user’s permanent cart stored in the database. 6. How Do You Store Frequently Accessed Product Images Efficiently? 7. What is Middleware in Django? Middleware is a layer between the request and the response. These are predefined in django: Authentication, Session, CSRF, and Security headers. Custom Middleware Example: class SimpleMiddleware: def __init__(self, get_response): self.get_response = get_response def __call__(self, request): print(“Before View:”, request.path) response = self.get_response(request) print(“After View:”, response.status_code) return response register in settings like settings.py → MIDDLEWARE = [‘myapp.middleware.SimpleMiddleware’, …] 8. How Do You Optimize Django ORM Queries? 9. How Do You Write Raw SQL Queries in Django? Two main ways of user raw or user cursor connection: users = UserProfile.objects.raw(“SELECT * FROM user WHERE active = %s”, [True]) from django.db import connection with connection.cursor() as cursor: cursor.execute(“SELECT id, name FROM user WHERE active = %s”, [True]) rows = cursor.fetchall() 10. What AWS Services Have You Used? 11. What is Load Balancing in AWS? Load balancing distributes incoming traffic across multiple servers. AWS provides Elastic Load Balancer (ELB): 12. What are the Types of JOIN Queries in SQL? In SQL, JOINs combine rows from two or more tables based on related columns. They allow you to fetch meaningful data by linking multiple tables together. Different types of JOINs define how records from one table are matched with records from another. 13. How Does LEFT JOIN Work? LEFT JOIN returns all rows from the left table and matching rows from the right. Non-matching → NULL. Example: SELECT e.name, d.dept_name FROM Employees e LEFT JOIN Departments d ON e.dept_id = d.id; 14. How Do You Implement Push Notifications in Django? 15. What is Redis, and How Did You Use It? Redis serves as a high-performance caching and message broker.Use cases in Django: Example (Django cache): from django.core.cache import cache def get_product(pid): key = f”product:{pid}” product = cache.get(key) if not product: product = Product.objects.get(id=pid) cache.set(key, product, 3600) return product Preparing for Python/Django backend interviews requires a balance of theory and practical knowledge. While Django and its ORM simplify a lot of work, interviewers often test your understanding of SQL, system design, caching, and cloud services like AWS. Therefore, practice coding problems, revisit core SQL queries, and explore concepts like load balancing, middleware, and caching. With consistent preparation, you’ll not only perform well in interviews but also become a more confident backend developer. See my previous Python Interview question.