Essential Python & Backend Interview Questions Every Junior Engineer Should Master

The author reflects on recent interview experiences at several tech companies and stresses the importance of coding daily and maintaining a visible Git history.

Python Syntax and Core Concepts

Mutable vs immutable types

Shallow copy vs deep copy and how to implement deepcopy

Difference between __new__() and __init__() Common design patterns

Encoding and decoding basics

List comprehensions vs generators

What decorators are and how to apply them after a function

Write a singleton using a decorator

Compare decorator‑based singleton with other implementations

Write a regular‑expression email validator

Explain garbage collection: reference counting, generational, and cyclic references

Differences between multiprocessing and multithreading; suitable workloads for each

Methods of inter‑process communication

Introduce coroutines and why they can be faster than threads

Difference between range and xrange In C, convert an IP address string (e.g., "172.0.0.1") to a 32‑bit binary number

Algorithm & Sorting Topics

Implement quicksort, heapsort; state the time complexities of common sorts and quicksort’s average vs worst‑case performance

Given an unsorted numeric list of length n, find all combinations spaced by d and analyze the algorithm’s complexity

Print all possible combinations of a list A = [A1, A2, …, An] One‑line Python to compute 1 + 2 + 3 + … + 10**8 Recursive palindrome check for a string

Detect a cycle in a singly linked list of unknown length

Sort a singly linked list using quicksort

Find the median of an unsorted numeric list and estimate its complexity

Traverse an unknown directory tree using two priority traversal methods

Network Fundamentals

Which OSI layer TCP/IP belongs to

Meaning of a persistent socket connection

Differences between select and epoll TCP vs UDP and the three‑way handshake/four‑way termination

Causes of excessive TIME_WAIT states

Full HTTP request‑response flow from client to server

HTTP methods (GET vs POST) and other request types

Understanding RESTful principles

Common HTTP status codes (e.g., 200, 403, 404, 504)

Database Topics

Types of MySQL locks and how deadlocks occur

Reasons and methods for sharding and partitioning

Differences among CHAR, VARCHAR, and TEXT JOIN types, especially LEFT JOIN behavior when the right table has no matching rows

Index types: B‑Tree vs hash and their storage differences

Write a query optimization example

Basics of NoSQL, differences from relational databases, and common Redis data structures

Linux & Git Commands

Frequently used Linux and Git commands and their purposes

Commands to view current processes and other common operations

Django Project Topics

Briefly describe your project role and contributions

Discuss the most challenging part of the project and your solution

Experience with Django admin source code, Flask source code, and open‑source understanding

Explain MVC/MTV architecture

How caching is used

Purpose of middleware

What CSRF is and how Django mitigates it; also XSS

Design a simple login flow

Difference between session and cookie; why sessions are considered secure

Roles of uWSGI and Nginx

Mastering these questions and regularly uploading code to GitHub can significantly improve interview performance for junior backend positions.