Table of Contents
Beginner Level (Core Fundamentals)
Intermediate Level (Problem Solving & Application)
Expert Level (System Design & Architecture)
Behavioral & IQ Questions
Beginner Level (Core Fundamentals)
Intermediate Level (Problem Solving & Application)
Expert Level (System Design & Architecture)
Behavioral & IQ Questions
1. Beginner Level: Core Fundamentals
These questions test your understanding of basic programming concepts, data structures, and algorithms.
Data Structures & Algorithms
Q1: Explain the difference between an Array and a Linked List. When would you use one over the other?
Example: Storing a list of usernames (Array) vs. implementing a stack where frequent insertions/deletions at one end are needed (Linked List).
Q2: What is a Hash Map? How does it achieve O(1) average time complexity for lookups?
Q3: Write a function to reverse a string in-place.
Q4: Implement a Stack using Arrays/Lists. Include push, pop, and peek operations.
Q5: What is the time complexity of searching a sorted array? How can you improve it? (Answer: Binary Search - O(log n)).
Q6: Traverse a Binary Tree in In-order, Pre-order, and Post-order.
Q7: Find the maximum depth (height) of a Binary Tree.
Q8: Check if two strings are Anagrams of each other.
Q1: Explain the difference between an Array and a Linked List. When would you use one over the other?
Example: Storing a list of usernames (Array) vs. implementing a stack where frequent insertions/deletions at one end are needed (Linked List).
Q2: What is a Hash Map? How does it achieve O(1) average time complexity for lookups?
Q3: Write a function to reverse a string in-place.
Q4: Implement a Stack using Arrays/Lists. Include push, pop, and peek operations.
Q5: What is the time complexity of searching a sorted array? How can you improve it? (Answer: Binary Search - O(log n)).
Q6: Traverse a Binary Tree in In-order, Pre-order, and Post-order.
Q7: Find the maximum depth (height) of a Binary Tree.
Q8: Check if two strings are Anagrams of each other.
Object-Oriented Programming (OOP)
Q9: Explain the four pillars of OOP with real-world analogies.
Example: Inheritance: A Car and Truck class inheriting common properties from a base Vehicle class.
Q10: What is the difference between an Abstract Class and an Interface? Provide a scenario for each.
Q11: What is Method Overriding vs. Method Overloading?
Q12: How does Polymorphism improve code maintainability?
Q9: Explain the four pillars of OOP with real-world analogies.
Example: Inheritance: A
CarandTruckclass inheriting common properties from a baseVehicleclass.
Q10: What is the difference between an Abstract Class and an Interface? Provide a scenario for each.
Q11: What is Method Overriding vs. Method Overloading?
Q12: How does Polymorphism improve code maintainability?
Basic Databases (SQL)
Q13: Write a SQL query to find the second highest salary from an Employees table.
Q14: Explain the difference between WHERE and HAVING clauses.
Q15: What is a JOIN? Describe INNER, LEFT, and FULL OUTER JOIN.
Q16: What is Database Normalization and why is it important?
Q13: Write a SQL query to find the second highest salary from an Employees table.
Q14: Explain the difference between WHERE and HAVING clauses.
Q15: What is a JOIN? Describe INNER, LEFT, and FULL OUTER JOIN.
Q16: What is Database Normalization and why is it important?
Programming Concepts
Q17: What is the difference between == and .equals() in Java?
Q18: Explain Pass by Value vs. Pass by Reference.
Q19: What are Exceptions? How do you handle them using try-catch-finally?
Q20: What are the key differences between a Process and a Thread?
Q17: What is the difference between == and .equals() in Java?
Q18: Explain Pass by Value vs. Pass by Reference.
Q19: What are Exceptions? How do you handle them using try-catch-finally?
Q20: What are the key differences between a Process and a Thread?
2. Intermediate Level: Problem Solving & Application
These questions assess your ability to apply fundamental knowledge to solve non-trivial problems, often involving algorithms and system-level thinking.
Algorithmic Problem Solving
Q21: Implement a function to check if a Linked List has a cycle. (Floyd's Cycle-Finding Algorithm).
Q22: Find the first non-repeating character in a string using efficient data structures.
Q23: Merge two sorted arrays into one sorted array.
Q24: Given a string, find the longest substring without repeating characters.
Q25: Implement a Binary Search Tree (BST) and write a function to check if it is valid.
Q26: Reverse a Linked List in-place.
Q27: Find all permutations of a given string.
Q28: Calculate the Fibonacci sequence using both iterative and recursive methods. Discuss the time/space complexity of each.
Q21: Implement a function to check if a Linked List has a cycle. (Floyd's Cycle-Finding Algorithm).
Q22: Find the first non-repeating character in a string using efficient data structures.
Q23: Merge two sorted arrays into one sorted array.
Q24: Given a string, find the longest substring without repeating characters.
Q25: Implement a Binary Search Tree (BST) and write a function to check if it is valid.
Q26: Reverse a Linked List in-place.
Q27: Find all permutations of a given string.
Q28: Calculate the Fibonacci sequence using both iterative and recursive methods. Discuss the time/space complexity of each.
Real-Life Scenarios & System Basics
Q29: How would you design a vending machine software system using OOP principles?
Q30: Describe how a web request works from typing a URL in the browser to seeing the page. (Hint: DNS, TCP, HTTP, Rendering).
Q31: What is REST? What are the characteristics of a RESTful API?
Q32: Explain the fundamental differences between SQL (e.g., MySQL) and NoSQL (e.g., MongoDB) databases. Give examples of when to use each.
Q33: What is Caching? Where and why would you implement it? (e.g., Redis, Memcached).
Q34: What is Load Balancing and what problems does it solve?
Q29: How would you design a vending machine software system using OOP principles?
Q30: Describe how a web request works from typing a URL in the browser to seeing the page. (Hint: DNS, TCP, HTTP, Rendering).
Q31: What is REST? What are the characteristics of a RESTful API?
Q32: Explain the fundamental differences between SQL (e.g., MySQL) and NoSQL (e.g., MongoDB) databases. Give examples of when to use each.
Q33: What is Caching? Where and why would you implement it? (e.g., Redis, Memcached).
Q34: What is Load Balancing and what problems does it solve?
Coding Examples & Debugging
Q35: Analyze the time complexity of a nested loop algorithm.
Q36: You have a function that is running slower than expected. What steps would you take to diagnose and fix the performance issue?
Q37: Write code that is vulnerable to a SQL Injection attack and then fix it. (Demonstrating use of Prepared Statements).
Q38: How would you efficiently sort a large file (10GB) that does not fit into memory? (Discuss External Sort).
Q35: Analyze the time complexity of a nested loop algorithm.
Q36: You have a function that is running slower than expected. What steps would you take to diagnose and fix the performance issue?
Q37: Write code that is vulnerable to a SQL Injection attack and then fix it. (Demonstrating use of Prepared Statements).
Q38: How would you efficiently sort a large file (10GB) that does not fit into memory? (Discuss External Sort).
Concurrency
Q39: What is a Deadlock? Describe the four necessary conditions for a deadlock with an example.
Q40: What is the difference between synchronized methods/blocks and volatile keyword in Java?
Q41: What is a Race Condition? Write a small code example that demonstrates one.
Q39: What is a Deadlock? Describe the four necessary conditions for a deadlock with an example.
Q40: What is the difference between synchronized methods/blocks and volatile keyword in Java?
Q41: What is a Race Condition? Write a small code example that demonstrates one.
3. Expert Level: System Design & Architecture
These questions evaluate your experience in designing scalable, reliable, and efficient large-scale systems.
Low-Level System Design (LLD)
Q42: Design a Parking Lot system. Identify core classes, objects, and their relationships.
Q43: Design a Chess game. How would you handle moves, game state, and special rules (castling, en passant)?
Q44: Design an online book reader system (like Kindle Cloud Reader).
Q45: Design a Blackjack (21) game simulation.
Q42: Design a Parking Lot system. Identify core classes, objects, and their relationships.
Q43: Design a Chess game. How would you handle moves, game state, and special rules (castling, en passant)?
Q44: Design an online book reader system (like Kindle Cloud Reader).
Q45: Design a Blackjack (21) game simulation.
High-Level System Design (HLD)
Q46: How would you design Twitter's feed? Discuss data models, fan-out approaches (push vs. pull), and scalability challenges.
Q47: Design a URL shortening service like TinyURL or Bitly.
Q48: Design Netflix or a video streaming service. Consider CDNs, video encoding, and recommendation systems.
Q49: Design a web crawler that can systematically browse the web at scale.
Q50: How would you design the backend for a ride-sharing service like Uber or Lyft? Discuss matching algorithms, real-time location tracking, and surge pricing.
Q46: How would you design Twitter's feed? Discuss data models, fan-out approaches (push vs. pull), and scalability challenges.
Q47: Design a URL shortening service like TinyURL or Bitly.
Q48: Design Netflix or a video streaming service. Consider CDNs, video encoding, and recommendation systems.
Q49: Design a web crawler that can systematically browse the web at scale.
Q50: How would you design the backend for a ride-sharing service like Uber or Lyft? Discuss matching algorithms, real-time location tracking, and surge pricing.
Scalability & Performance
Q51: What is Database Sharding? What are the different sharding strategies?
Q52: Explain the CAP Theorem. Can you have a CA system?
Q53: What are Microservices? What are the trade-offs compared to a Monolithic architecture?
Q54: How does a Message Queue (e.g., Kafka, RabbitMQ) help in building decoupled and scalable systems?
Q55: What are the different caching strategies? (e.g., Write-through, Write-around, Write-back).
Q51: What is Database Sharding? What are the different sharding strategies?
Q52: Explain the CAP Theorem. Can you have a CA system?
Q53: What are Microservices? What are the trade-offs compared to a Monolithic architecture?
Q54: How does a Message Queue (e.g., Kafka, RabbitMQ) help in building decoupled and scalable systems?
Q55: What are the different caching strategies? (e.g., Write-through, Write-around, Write-back).
4. Behavioral & IQ Questions
These questions assess your soft skills, problem-solving approach, and cultural fit.
Situational & Behavioral
Q56: Tell me about a time you had a disagreement with a teammate. How did you handle it?
Q57: Describe the most technically challenging project you've worked on. What was your role?
Q58: How do you prioritize tasks when working on multiple projects with tight deadlines?
Q59: Tell me about a time you failed. What did you learn from it?
Q60: How do you stay updated with the latest technology trends?
Q56: Tell me about a time you had a disagreement with a teammate. How did you handle it?
Q57: Describe the most technically challenging project you've worked on. What was your role?
Q58: How do you prioritize tasks when working on multiple projects with tight deadlines?
Q59: Tell me about a time you failed. What did you learn from it?
Q60: How do you stay updated with the latest technology trends?
Analytical & IQ Puzzles
Q61: There are 100 identical coins on a table. 10 are facing heads up and 90 are tails up. You are blindfolded and cannot tell by touch. How can you split them into two piles so that each pile has the same number of heads?
Answer: Make one pile of 10 coins and another of 90. Flip all coins in the pile of 10.
Q62: You have two jugs: one that holds 5 liters and one that holds 3 liters. How do you measure out exactly 4 liters of water?
Q63: A man has to get a fox, a chicken, and a sack of corn across a river. His boat can only carry himself and one other thing. If the fox and the chicken are left alone, the fox will eat the chicken. If the chicken and the corn are left alone, the chicken will eat the corn. How does the man get all three across safely?
Q64: Why are manhole covers round?
Q65: How many golf balls can fit in a school bus?
Q61: There are 100 identical coins on a table. 10 are facing heads up and 90 are tails up. You are blindfolded and cannot tell by touch. How can you split them into two piles so that each pile has the same number of heads?
Answer: Make one pile of 10 coins and another of 90. Flip all coins in the pile of 10.
Q62: You have two jugs: one that holds 5 liters and one that holds 3 liters. How do you measure out exactly 4 liters of water?
Q63: A man has to get a fox, a chicken, and a sack of corn across a river. His boat can only carry himself and one other thing. If the fox and the chicken are left alone, the fox will eat the chicken. If the chicken and the corn are left alone, the chicken will eat the corn. How does the man get all three across safely?
Q64: Why are manhole covers round?
Q65: How many golf balls can fit in a school bus?
5. Beginner Level (Continued)
Basic Programming & Logic
Q66: What is a recursive function? Write a simple example and explain the base case and recursive case.
Q67: How do you swap two numbers without using a temporary variable?
Q68: Check if a given number is a Prime Number.
Q69: Print a Pyramid pattern using asterisks
*with code.Q70: What is the difference between a Compiler and an Interpreter?
Q71: Explain the concept of "Big O Notation" in simple terms. Why is it important?
Q72: What is a Loop Invariant? Provide an example for a simple sorting algorithm.
Basic Web Technologies
Q73: What is the difference between HTTP GET and POST methods?
Q74: What are Cookies and Sessions? How do they differ?
Q75: Briefly explain what JavaScript is and its role in web development.
Version Control (Git)
Q76: Explain the difference between
git mergeandgit rebase.Q77: What is a
git conflictand how do you resolve it?Q78: How do you revert a commit that has already been pushed and made public?
6. Intermediate Level (Continued)
Data Structures Deep Dive
Q79: Implement a Queue using two Stacks.
Q80: Find the Middle Element of a Linked List in a single pass.
Q81: Check if a Binary Tree is a mirror image of itself (symmetric).
Q82: Given a list of daily stock prices, find the maximum profit achievable from one buy and one sell transaction.
Q83: Implement a Least Recently Used (LRU) Cache data structure. This is a classic problem combining HashMap and Doubly Linked List.
Q84: Sort an array of 0s, 1s, and 2s (Dutch National Flag problem) in a single pass.
Q85: Given a set of time intervals, merge all overlapping intervals.
Database & SQL Scenarios
Q86: What are Database Indexes? How do they work and what are the trade-offs?
Q87: Write a SQL query to find employees who have the highest salary in each department.
Q88: What is a "self-join"? Provide a practical example (e.g., finding employees and their managers from the same table).
Q89: Explain Database Transactions and the ACID properties.
Q90: What is the N+1 Query Problem in ORMs? How can you solve it? (e.g., using eager loading).
Concurrency & Multithreading
Q91: What is a Semaphore? How is it different from a Mutex?
Q92: What is Thread Pooling? Why is it used?
Q93: Write a simple Producer-Consumer problem solution using threads.
Q94: What is "Starvation" in the context of multithreading?
Networking & APIs
Q95: Explain the difference between TCP and UDP protocols.
Q96: What are HTTP Status Codes? Explain 200, 201, 400, 401, 403, 404, 500.
Q97: What is the difference between SOAP and REST APIs?
Q98: What is WebSockets? How is it different from HTTP?
7. Expert Level (Continued)
Low-Level System Design (LLD)
Q99: Design a Logger system that can log messages with different severity levels (e.g., INFO, DEBUG, ERROR) to multiple outputs (console, file, network).
Q100: Design a Task Scheduler (like Cron) that can execute tasks at specified intervals.
Q101: Design a global, thread-safe In-Memory Cache (like a simplified Redis).
Q102: Design the data structures for a social network (hint: graph). How would you find the shortest path between two users? (BFS).
High-Level System Design (HLD)
Q103: Design a distributed Key-Value store (like Amazon DynamoDB or Redis Cluster).
Q104: How would you design a search autocomplete (typeahead) feature for a search engine?
Q105: Design a notification service for a mobile app that can push to millions of devices.
Q106: Design an API Rate Limiter for a public API (e.g., using Token Bucket or Leaky Bucket algorithm).
Q107: How would you design a system like Pastebin where users can upload text and share it via a unique URL?
Q108: Design an analytics system that can track click events on a website at scale (billions of events per day).
Scalability, Reliability, & DevOps
Q109: What is Consistent Hashing and why is it important in distributed systems?
Q110: Explain the concept of "Leader Election" in distributed systems.
Q111: What is a Circuit Breaker pattern? How does it prevent cascading failures?
Q112: What is Blue-Green Deployment? What are its advantages?
Q113: How does Docker work? What problem does it solve?
Q114: Explain the difference between Kubernetes and Docker Swarm.
8. Coding Problem Patterns (A Must-Know List)
Recognizing common patterns is key to solving coding problems efficiently.
Q115: Two Pointers: Given a sorted array, find two numbers that add up to a specific target.
Q116: Sliding Window: Given an array of integers and a number
k, find the maximum sum of any contiguous subarray of sizek.Q117: BFS (Breadth-First Search) & DFS (Depth-First Search): Find the shortest path in a maze. Clone a graph.
Q118: Binary Search: Given a sorted array that is rotated at some pivot, find a target value (e.g.,
[4,5,6,7,0,1,2], target=0).Q119: Top K Elements: Find the top K frequent elements in an array. (Solution: Min-Heap + HashMap).
Q120: Dynamic Programming: Find the longest increasing subsequence. The classic Fibonacci is just the start.
Q121: Backtracking: Solve the N-Queens puzzle. Generate all valid combinations of n-pairs of parentheses.
Q122: Union Find (Disjoint Set): Count the number of connected components in an undirected graph.
Q123: Trie (Prefix Tree): Implement an autocomplete system using a Trie.
Q124: Graph Algorithms (Dijkstra's): Find the shortest path in a weighted graph.
9. Real-Life Scenario & Troubleshooting
Q125: A user reports the website is slow. Walk me through your step-by-step debugging process from frontend to backend to database.
Q126: You push a new feature to production, and it immediately causes a 50% error rate. What's your immediate action plan? (Rollback, isolate, check logs).
Q127: How would you troubleshoot a memory leak in a Java application?
Q128: You notice the database CPU is consistently at 100%. What are the potential causes and how would you investigate?
Q129: Describe how you would do code reviews. What are the most important things you look for?
Q130: How do you ensure the quality of your code before deployment? (Unit tests, Integration tests, CI/CD).
10. Modern Concepts & Trivia
Q131: What is the difference between
let,var, andconstin JavaScript?Q132: What is a Promise in JavaScript? How is it different from a Callback?
Q133: Explain the concept of "Immutability". Why is it important in frameworks like React?
Q134: What is the Virtual DOM?
Q135: What are the core principles of Functional Programming?
Q136: What is Machine Learning? Explain a simple model like Linear Regression to a 10-year-old.
Q137: What is Blockchain, in simple terms?
Q138: What are the differences between SQL, NewSQL, and NoSQL databases?
Q139: What is Serverless Architecture (e.g., AWS Lambda)?
Q140: What is the difference between Authentication and Authorization?
Q141: What is OAuth 2.0 flow?
Q142: What is JWT (JSON Web Token)?
Q143: What are some common security vulnerabilities in web applications? (OWASP Top 10: SQL Injection, XSS, CSRF).
Q144: What is the Single Responsibility Principle?
Q145: What is the Dependency Injection principle?
Q146: What is the difference between a Monolith and Microservices?
Q147: What is an API Gateway?
Q148: What is the difference between a Full Stack, Frontend, and Backend developer?
Q149: What is your favorite programming language and why? (A common opener to gauge passion and depth).
Q150+: What new technology or framework are you most excited about today?
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Md. Mominul Islam