70+ Backend Developer Interview Questions and Answers for Freshers

Reverse words in a string while handling leading, trailing, and multiple spaces.

• Split the input string by spaces to get individual words

• Reverse the order of the words

• Join the reversed words with a single space in between

• Handle leading, trailing, and multiple spaces appropriately

Reverse a singly linked list of integers and return the head of the reversed linked list.

• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Keep track of the previous, current, and next nodes while reversing the linked list.

• Update the head of the reversed linked list as the last node encountered during the reversal process.

Sort an array of 0's, 1's, and 2's using two pointer approach.

• Initialize two pointers, one at the beginning and one at the end of the array.

• Traverse the array and swap 0's to the beginning and 2's to the end using the pointers.

• Stop when the pointers meet or cross each other.

Search for an element in a rotated sorted array using binary search with pivot.

• Find the pivot element using binary search.

• Compare the target element with the first element of the array to determine which half to search.

• Perform binary search on the selected half of the array.

• Repeat until the target element is found or the array is exhausted.

Mongo query to increase age by 20% for documents with age field

• Use $exists operator to filter documents with age field

• Use $mul operator to increase age by 20%

• Example: db.users.updateMany({ age: { $exists: true } }, { $mul: { age: 1.2 } })

Search an element in an infinite sorted array using binary search.

• Initialize low as 0 and high as 1.

• Double the high index until arr[high] is greater than the target element.

• Perform binary search between low and high indexes.

Java is a popular programming language used for developing various applications.

• Java is a high-level, object-oriented programming language.

• Float is a single-precision 32-bit floating point data type, while double is a double-precision 64-bit floating point data type.

• Java has three types of loops: for, while, and do-while.

• While loop checks the condition before executing the code block, whereas do-while loop executes the code block first and then checks the condition.

• For loop i...read more

ID selector is used to select an element with a specific ID attribute in CSS.

• ID selector is denoted by '#' followed by the ID name.

• ID should be unique on a page.

• ID selector has higher specificity than class selector.

• Example: #header { color: blue; }

Over-indexing in MongoDB can negatively impact performance by increasing memory usage and slowing down query execution.

• Over-indexing can lead to increased memory usage as each index consumes memory.

• Having too many indexes can slow down write operations as each index needs to be updated when a document is inserted, updated, or deleted.

• To prevent over-indexing, carefully analyze query patterns and create indexes only for fields that are frequently queried.

• Regularly review and r...read more

Use the KEYS command in Redis to retrieve all keys containing a specific substring.

• Use the KEYS command followed by the pattern '*xyz*' to retrieve all keys containing the substring 'xyz'.

• Be cautious when using the KEYS command as it can be resource-intensive on large datasets.

• Consider using SCAN command for better performance when dealing with large datasets.

Key factors include data modeling, normalization, indexing, scalability, and performance.

• Consider data modeling to ensure efficient storage and retrieval of data.

• Normalize the database to reduce redundancy and improve data integrity.

• Use indexing to speed up data retrieval operations.

• Design for scalability to accommodate future growth and changes.

• Optimize for performance by considering query optimization and data caching.

Promises are objects representing the eventual completion or failure of an asynchronous operation, while callbacks are functions passed as arguments to be executed after a task is completed.

• Promises allow chaining multiple asynchronous operations, while callbacks can lead to callback hell.

• Promises have built-in error handling through .catch(), while callbacks rely on error-first callbacks.

• Promises are easier to read and maintain due to their sequential nature, while callbacks...read more

I believe no-code tools like XANO are great for rapid prototyping and simplifying development processes.

• No-code tools like XANO allow for faster development by eliminating the need for manual coding

• They are great for prototyping and testing ideas quickly

• XANO specifically offers a visual interface for building backend logic without writing code

• I have used XANO in a few projects and found it to be user-friendly and efficient

Yes, I have experience with Xano, a no-code backend development platform that simplifies API creation and database management.

• Utilized Xano to build a RESTful API for a mobile application, streamlining data retrieval and management.

• Leveraged Xano's database features to create and manage complex data relationships without writing SQL queries.

• Integrated third-party services like Stripe for payment processing using Xano's built-in connectors.

• Created custom business logic using X...read more

ShallowCopy copies only the reference of an object while DeepCopy creates a new object with a new reference.

• ShallowCopy creates a new reference to the same object, so changes made to the copy will reflect in the original object.

• DeepCopy creates a new object with a new reference, so changes made to the copy will not reflect in the original object.

• ShallowCopy is faster and less memory-intensive than DeepCopy.

• DeepCopy is necessary when you need to modify the copied object withou...read more

The request-response cycle in node.js involves a client sending a request to a server, which processes the request and sends back a response.

• Client sends a request to the server using HTTP methods like GET, POST, PUT, DELETE.

• Server receives the request, processes it, and generates a response.

• The response is sent back to the client, typically in the form of HTML, JSON, or other data formats.

• Node.js uses event-driven, non-blocking I/O model to handle multiple requests efficient...read more

Different authentication methods include OAuth, JWT, Basic Auth, and OAuth2.

• OAuth: Allows third-party applications to access resources without sharing credentials.

• JWT (JSON Web Tokens): Securely transmit information between parties as a JSON object.

• Basic Auth: Sends user credentials in the header of each request.

• OAuth2: Authorization framework that enables a third-party application to obtain limited access to an HTTP service.

I would rate my proficiency in data structures and algorithms as an 8.

• I have a strong understanding of common data structures like arrays, linked lists, trees, and graphs.

• I am proficient in implementing algorithms like sorting, searching, and dynamic programming.

• I have experience solving algorithmic problems on platforms like LeetCode and HackerRank.

Middleware facilitates communication between applications and databases, while DBMS and RDBMS manage data storage and retrieval.

• Middleware: Acts as a bridge between different applications or services, enabling them to communicate and share data. Example: Express.js in Node.js.

• Database Management System (DBMS): Software that manages databases, allowing for data storage, retrieval, and manipulation. Example: MongoDB.

• Relational Database Management System (RDBMS): A type of DBMS ...read more

Find the largest Jumping number less than the given number in Java.

• Create a function to check if a number is a Jumping number.

• Iterate from the given number to 0 and find the largest Jumping number.

• Return the largest Jumping number found.

Steps to connect PostgreSQL to Django

• Install psycopg2 package using pip

• Update DATABASES setting in Django settings.py file

• Specify database name, user, password, host, and port in settings.py

• Run migrations to create necessary database tables

• Test the connection by running Django server

OOPs concepts include encapsulation, inheritance, polymorphism, and abstraction, crucial for structured programming.

• Encapsulation: Bundling data and methods. Example: A class 'Car' with properties like 'speed' and methods like 'accelerate()'.

• Inheritance: Deriving new classes from existing ones. Example: 'ElectricCar' inherits from 'Car', adding features like 'batteryCapacity'.

• Polymorphism: Methods behaving differently based on the object. Example: A method 'start()' in 'Car' ...read more

Implementing Snake and Ladder in 2D using Pandas DataFrame allows for easy tracking of player positions and game state.

• Game Board Representation: Use a 10x10 DataFrame to represent the board, with cells indicating positions, snakes, and ladders.

• Player Movement: Update player positions based on dice rolls, modifying the DataFrame to reflect their new locations.

• Snakes and Ladders Logic: Implement logic to move players down snakes or up ladders by mapping specific cells to their...read more

My approach for Heavy Data Handling involves optimizing database queries, using indexing, caching, and implementing efficient algorithms.

• Optimizing database queries by using proper indexing and avoiding unnecessary joins

• Implementing caching mechanisms to reduce the load on the database

• Using efficient algorithms for data processing and manipulation

• Batch processing large datasets to minimize resource usage

• Implementing data partitioning and sharding for scalability

• Utilizing para...read more

C is a procedural programming language while Java is an object-oriented programming language.

• C is a low-level language with manual memory management, while Java is a high-level language with automatic memory management.

• C uses pointers extensively, while Java does not support pointers.

• C is platform-dependent, while Java is platform-independent due to its bytecode.

• C does not have built-in support for threads, while Java has built-in support for multithreading.

• C has a simpler sy...read more

Struct is a value type while class is a reference type in C#.

• Structs are stored on the stack while classes are stored on the heap.

• Structs cannot be inherited while classes can be inherited.

• Structs do not support destructors while classes do.

• Structs are used for small data structures while classes are used for larger, more complex objects.

• Example of struct: struct Point { public int X; public int Y; }

• Example of class: class Person { public string Name; public int Age; }

Yes, PHP is a server-side scripting language and MySQL is a relational database management system commonly used together for web development.

• PHP is used to create dynamic web pages and can be embedded in HTML code

• MySQL is used to store and manage data in a relational database

• PHP can connect to MySQL to retrieve and manipulate data

• Examples of websites built with PHP and MySQL include Facebook and WordPress