40+ Backend Developer Intern Interview Questions and Answers

Backend Developer Intern interview questions on HTTP methods, MVC, PHP framework, SESSION, COOKIE, and SQL queries.

• GET is used to retrieve data from a server while POST is used to submit data to a server

• MVC stands for Model-View-Controller and is a software design pattern used for separating concerns in an application

• PHP frameworks include Laravel, CodeIgniter, and Symfony

• SESSION and COOKIE are used for storing data on the client-side

• SQL queries are used for interacting with ...read more

Primitive data types are passed by value, while non-primitive data types are passed by reference. Changes in value can occur after downstream operations for non-primitive data types.

• Primitive data types (int, float, char, etc.) are passed by value, meaning a copy of the value is passed to the method. Changes made to the parameter inside the method do not affect the original value.

• Non-primitive data types (objects, arrays, etc.) are passed by reference, meaning the memory addr...read more

express.json middleware is used to parse JSON data in the request body.

• It is used to parse JSON data in the request body.

• It is a built-in middleware function in Express.

• It sets the Content-Type header to application/json.

• It parses the JSON data and populates the req.body object with the parsed data.

• It is used in conjunction with the bodyParser middleware.

Printing diagonal elements of an array from right top corner to left bottom corner.

• Iterate through the rows and columns of the array

• Print the diagonal elements using row and column indices

• Start from the right top corner and move towards the left bottom corner

Different sorting methods are beneficial in different scenarios based on factors like time complexity, space complexity, and input size.

• Quick Sort: Best for large datasets due to its average time complexity of O(n log n)

• Bubble Sort: Simple and easy to implement, but inefficient for large datasets with its time complexity of O(n^2)

• Merge Sort: Stable and efficient for large datasets with its time complexity of O(n log n)

• Insertion Sort: Efficient for small datasets or nearly sor...read more

Use process of elimination by tasting from jars to identify contents.

• Taste from the jar labeled 'Mixed'. If it tastes like chocolate, then it must be the mixed jar. If it tastes like vanilla, then it must be the vanilla jar. The remaining jar is chocolate.

• If the 'Mixed' jar tastes like vanilla, then the 'Vanilla' jar is the one labeled 'Mixed'. The remaining jar is chocolate.

• This method requires only 1 taste to identify each jar correctly.

Spring is a framework for building Java applications, while Spring Boot is an extension that simplifies the setup and configuration process.

• Spring is a comprehensive framework for building Java applications, providing features like dependency injection, aspect-oriented programming, and more.

• Spring Boot is an extension of the Spring framework that aims to simplify the setup and configuration process by providing defaults for common configurations.

• Cloud computing refers to the ...read more

TCP/IP is a protocol suite that defines how data is transmitted over the internet.

• TCP/IP has four layers: application, transport, internet, and network access.

• The application layer is responsible for user interaction, while the network access layer deals with hardware.

• The transport layer ensures reliable data transfer, while the internet layer handles routing.

• Examples of protocols in TCP/IP include HTTP, FTP, TCP, and IP.

• TCP/IP is the foundation of the internet and is used fo...read more

Web Sockets is a communication protocol that provides full-duplex communication channels over a single TCP connection.

• Web Sockets allow for real-time, bi-directional communication between a client and a server.

• They are commonly used in chat applications, online gaming, and live data streaming.

• Web Sockets use the ws:// or wss:// protocol scheme in URLs.

• The protocol is initiated with a handshake between the client and server.

• Once the connection is established, data can be sent ...read more

Javascript is single threaded.

• Javascript is single threaded, meaning it can only execute one piece of code at a time.

• This is because of the event loop in Javascript, which manages the execution of code.

• Asynchronous operations in Javascript, like setTimeout or AJAX requests, are handled by the event loop.

• Web Workers can be used to achieve multithreading in Javascript for CPU-intensive tasks.

Indexing typically uses data structures like B-trees or hash tables for efficient retrieval, with time complexity of O(log n) or O(1) respectively.

• Common data structures for indexing include B-trees and hash tables

• B-trees are typically used for indexing in databases due to their balanced nature and efficient search operations

• Hash tables are used for indexing in scenarios where constant time lookup is desired, but may have collisions requiring additional handling

JavaScript is a high-level, interpreted programming language used for creating interactive websites and web applications.

• JavaScript is primarily used for client-side web development.

• It can also be used for server-side development with Node.js.

• JavaScript is versatile and can be used for creating animations, games, and mobile apps.

• It supports object-oriented, imperative, and functional programming styles.

• Common JavaScript frameworks/libraries include React, Angular, and Vue.

ACID properties are a set of properties that guarantee reliability and consistency in database transactions.

• Atomicity: Ensures that either all operations in a transaction are completed successfully or none at all.

• Consistency: Ensures that the database remains in a consistent state before and after the transaction.

• Isolation: Ensures that the execution of multiple transactions concurrently does not interfere with each other.

• Durability: Ensures that once a transaction is committ...read more

MERN stack uses MongoDB, Express, React, and Node.js frameworks.

• MongoDB - NoSQL database used for storing data

• Express - Web application framework for Node.js

• React - JavaScript library for building user interfaces

• Node.js - JavaScript runtime environment for server-side development

Time complexity of recursive fibonacci code is O(2^n)

• The time complexity of a recursive fibonacci code is exponential, O(2^n)

• This is because each call branches into two recursive calls, leading to exponential growth

• For example, calculating fibonacci(5) would result in 15 function calls

Count the number of islands in a binary matrix.

• Traverse the matrix and for each 1 encountered, perform DFS to mark all connected 1s as visited.

• Increment the island count for each new DFS traversal.

• Use a visited matrix to keep track of visited cells.

• Consider diagonal cells as connected if required.

• Optimize by using Union-Find data structure.

LCA of a binary tree is the lowest common ancestor of two nodes in the tree.

• Traverse the tree from the root node to find the paths from root to the two given nodes.

• Compare the paths to find the last common node, which is the LCA.

• Use recursion to solve the problem efficiently.

• Handle edge cases like if one of the nodes is the ancestor of the other.

Exception handling in Spring Boot microservices involves using @ControllerAdvice and @ExceptionHandler annotations.

• Use @ControllerAdvice to define global exception handling for all controllers

• Use @ExceptionHandler to handle specific exceptions within a controller

• Return appropriate HTTP status codes and error messages in the response

ASP.NET is a web application framework developed by Microsoft for building dynamic web sites, web applications, and web services.

• Developed by Microsoft

• Used for building dynamic web sites, web applications, and web services

• Supports multiple programming languages such as C# and VB.NET

• Includes features like authentication, authorization, and caching

• Consists of ASP.NET Web Forms, ASP.NET MVC, and ASP.NET Web API

ASP.NET is a web application framework developed by Microsoft for building dynamic web sites, web applications, and web services.

• Developed by Microsoft

• Used for building dynamic web sites, web applications, and web services

• Supports multiple programming languages like C# and VB.NET

• Includes features like authentication, authorization, and caching

• Consists of ASP.NET Web Forms, ASP.NET MVC, and ASP.NET Web API

I am proficient in JavaScript for frontend development.

• Experienced in building interactive web applications using JavaScript

• Familiar with popular frontend frameworks like React and Angular

• Skilled in implementing responsive design and user-friendly interfaces

Left, right, top, and bottom views of a Binary Tree

• Left view: Nodes visible when seen from the left side

• Right view: Nodes visible when seen from the right side

• Top view: Nodes visible when seen from the top

• Bottom view: Nodes visible when seen from the bottom

SQL Injection is a type of cyber attack where malicious SQL statements are inserted into an entry field for execution.

• SQL Injection is a common web application security vulnerability.

• Attackers can inject malicious SQL code into input fields to manipulate the database.

• It can lead to unauthorized access, data leakage, and data manipulation.

• Example: Entering 'OR 1=1' in a login form to bypass authentication.

Logs are records of events or actions that occur in a system. Designing Redis databases involves considering data structures and access patterns.

• Logs are used for troubleshooting, monitoring, and auditing purposes.

• Designing Redis databases involves identifying the data structures needed to store and retrieve logs efficiently.

• Consider using Redis data types like lists, sets, or sorted sets to store logs based on specific requirements.

• Use appropriate Redis commands and data str...read more

Microservices in JavaScript are small, independent, and loosely coupled services that work together to form a larger application.

• Microservices are designed to be modular and scalable

• Each microservice performs a specific task and communicates with other microservices through APIs

• They can be written in different programming languages and can run on different servers

• Examples of microservices in JavaScript include Netflix, PayPal, and Uber

Indexing in DBMS is a technique used to improve the performance of queries by allowing faster retrieval of data.

• Indexes are data structures that store a small portion of the table data in an optimized format for quick retrieval.

• They help in speeding up data retrieval operations like SELECT, UPDATE, DELETE queries.

• Examples of indexes include primary keys, unique keys, and composite keys.

Design API for executing Python code remotely.

• Use RESTful API endpoints to send and receive code snippets.

• Include authentication mechanisms to ensure secure code execution.

• Implement error handling to handle exceptions and provide meaningful error messages.

• Consider implementing rate limiting to prevent abuse of the API.

• Use libraries like Flask or Django for building the API.

• Example: POST request to /execute with Python code in the request body.

• Example: GET request to /status/{...read more

Filter, map, and reduce are higher-order functions commonly used in functional programming to manipulate arrays.

• Filter: Creates a new array with elements that pass a certain condition

• Map: Transforms each element in an array into a new element based on a function

• Reduce: Reduces an array to a single value by applying a function to each element

Find the median of a stream of numbers.

• Maintain two heaps, one max heap for the lower half and one min heap for the upper half.

• If the size of the heaps differ by more than 1, balance them by moving the root of one heap to the other.

• If the size of the heaps are equal, the median is the average of the roots of the two heaps. Otherwise, the median is the root of the heap with more elements.

Stream API is a powerful tool in Java for processing collections of objects.

• Advantages include concise code, improved performance, and ease of parallel processing.

• Uses include filtering, mapping, sorting, and reducing data in collections.

• Example: stream.filter(x -> x > 5).map(x -> x * 2).collect(Collectors.toList());

Object-oriented programming concepts that focus on organizing code into objects with properties and behaviors.

• Encapsulation: Bundling data and methods that operate on the data into a single unit (object).

• Inheritance: Allowing a class (subclass) to inherit properties and behaviors from another class (superclass).

• Polymorphism: Objects of different classes can be treated as objects of a common superclass.

• Abstraction: Hiding complex implementation details and showing only the nec...read more

Object orientation is a programming paradigm that organizes software design around objects and data rather than actions and logic.

• Objects are instances of classes that encapsulate data and behavior

• Encapsulation hides the internal state of an object and only allows access through methods

• Inheritance allows classes to inherit attributes and methods from other classes

• Polymorphism allows objects of different classes to be treated as objects of a common superclass

• Object orientation...read more

Processes are independent instances of a program, while threads are smaller units within a process sharing resources.

• Processes have their own memory space, while threads share the same memory space within a process.

• Processes are heavyweight, requiring more resources, while threads are lightweight.

• Processes communicate with each other through inter-process communication mechanisms, while threads can communicate directly.

• Example: A web browser running multiple tabs is a process...read more

MySQL is a popular open-source relational database management system.

• MySQL is used to store and manage data in a structured format.

• It uses SQL (Structured Query Language) for querying and managing the database.

• MySQL is commonly used in web applications for data storage and retrieval.

• It supports features like transactions, indexing, and stored procedures.

• Examples of MySQL-based applications include WordPress, Joomla, and Magento.

The DB schema of my project includes tables for users, products, orders, and reviews.

• Users table with columns for user ID, username, email, password

• Products table with columns for product ID, name, price, description

• Orders table with columns for order ID, user ID, product ID, quantity

• Reviews table with columns for review ID, product ID, user ID, rating, comment

The time complexity of MongoDB insert method is O(1) on average.

• Inserting a document into a MongoDB collection has a constant time complexity of O(1) on average.

• This is because MongoDB uses a B-tree data structure to store documents, allowing for fast insertion operations.

• The actual time complexity may vary depending on factors such as the size of the collection and the available system resources.

Detect loop in linked list

• Use two pointers, one moving one step at a time and the other moving two steps at a time

• If there is a loop, the two pointers will eventually meet

• If any of the pointers reach the end of the list, there is no loop

SQL is a relational database management system, while NoSQL is a non-relational database management system.

• SQL databases are table-based and have a predefined schema, while NoSQL databases are document-based, key-value pairs, graph databases, or wide-column stores.

• SQL databases are suitable for complex queries and transactions, while NoSQL databases are better for large amounts of data and scalable applications.

• Examples of SQL databases include MySQL, Oracle, and PostgreSQL, ...read more

Types of mapping in hibernate include one-to-one, one-to-many, many-to-one, and many-to-many mappings.

• One-to-one mapping: Each instance of one entity is associated with exactly one instance of another entity.

• One-to-many mapping: Each instance of one entity is associated with multiple instances of another entity.

• Many-to-one mapping: Multiple instances of one entity are associated with exactly one instance of another entity.

• Many-to-many mapping: Multiple instances of one entity...read more

To print the date time year, use a programming language's built-in date and time functions.

• Use a programming language like Python, JavaScript, or Java to get the current date and time.

• Format the date time to include the year component.

• Print the formatted date time year to the console or output it in some other way.

Root cause analysis involves identifying the underlying reason for an issue.

• Identify the problem or issue that needs to be addressed

• Gather relevant data and information related to the issue

• Analyze the data to determine potential causes of the issue

• Consider all possible factors that could have contributed to the problem

• Develop a hypothesis or theory about the root cause

• Test the hypothesis to confirm the root cause

• Implement a solution to address the root cause and prevent futur...read more

Count the number of islands in a 2D grid of '1's and '0's.

• Iterate through the grid and for each '1' encountered, perform a depth-first search to mark all connected '1's as visited.

• Increment the island count for each unvisited '1' encountered during the iteration.

• Example: Input grid = [['1','1','0','0'],['1','1','0','0'],['0','0','1','0'],['0','0','0','1']], Output = 3

Reverse a string by iterating through the characters and swapping them

• Create an empty string to store the reversed string

• Iterate through the characters of the input string from end to start

• Append each character to the empty string to reverse the string

A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward.

• Palindrome examples: 'radar', 'madam', 'level', '12321'

• Palindrome can be a single word or a phrase

• Palindrome ignores spaces, punctuation, and capitalization

Object-oriented programming is a programming paradigm based on the concept of objects, which can contain data and code.

• OOP focuses on creating objects that interact with each other to solve problems

• Encapsulation: bundling data and methods that operate on the data into a single unit (object)

• Inheritance: allows new classes to be created based on existing classes

• Polymorphism: the ability for objects to be treated as instances of their parent class

OOPs concept is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.

• OOPs stands for Object-Oriented Programming

• Key concepts include classes, objects, inheritance, polymorphism, and encapsulation

• Classes are blueprints for creating objects, which are instances of classes

• Inheritance allows a class to inherit properties and behavior from another class

• Polymorphism allows objects to be treated as in...read more