Xcelore Interview Questions and Answers

Q1. NodeJS Event Loop in Depth
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Q2. Explain about API Security
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Q3. Explain Middlewares in NodeJS Express
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Q4. Database aggregations, indexing, optimization related questions
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Q5. Basic SQl queries
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Q6. Object Oriented Programming Basic Concepts
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Q1. Define the feature of java 8 feature.
Ans. 
Java 8 introduced significant features like lambdas, streams, and new APIs that enhance productivity and code readability.
• Lambda Expressions: Enable concise representation of functional interfaces. Example: (a, b) -> a + b.

• Streams API: Facilitates functional-style operations on collections. Example: list.stream().filter(x -> x > 10).collect(Collectors.toList()).

• Default Methods: Allow interfaces to have method ...read more
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Q2. Define spring boot artictecture
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Spring Boot is a framework that simplifies Java application development with built-in features and microservices architecture.
• Microservices Architecture: Spring Boot is designed for building microservices, allowing developers to create standalone applications.

• Convention over Configuration: It reduces the need for extensive configuration by providing default settings, making it easier to get started.

• Embedded Servers: Sp...read more
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Q1. All questions about my tech stacks and their requirements.
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Q2. Few basic coding & machine coding questions and HR questions.
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Q1. What are Promises and Async Await?
Ans. 
Promises and Async/Await are JavaScript features for handling asynchronous operations more efficiently and readably.
• A Promise is an object representing the eventual completion (or failure) of an asynchronous operation.

• Promises have three states: pending, fulfilled, and rejected.

• Example of a Promise: const myPromise = new Promise((resolve, reject) => { /* async operation */ });

• Async/Await is syntactic sugar built on ...read more
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Q2. Question on fetch API
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Q1. What is Hoisting?
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during compilation.
• Variable and function declarations are hoisted to the top of their scope.

• Only declarations are hoisted, not initializations.

• Function declarations take precedence over variable declarations.

• Hoisting can lead to unexpected behavior if not understood properly.
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Q2. What is Closures?
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Closures are functions that have access to variables from their containing scope even after the parent function has finished executing.
• Closures allow functions to maintain access to variables from their outer scope

• They are created when a function is defined within another function

• Closures are commonly used in event handlers and callbacks
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Q3. What is Promises?
Ans. 
Promises are a way to handle asynchronous operations in JavaScript, providing a cleaner alternative to callbacks.
• Promises represent the eventual completion (or failure) of an asynchronous operation.

• They allow you to chain multiple asynchronous operations together.

• Promises have states: pending, fulfilled, or rejected.

• You can handle the result of a promise using .then() and .catch() methods.

• Example: const myPromise = new...read more
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Q4. What is Callback Hell?
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Callback Hell is a situation in asynchronous programming where multiple nested callbacks make the code hard to read and maintain.
• Occurs when multiple asynchronous operations are nested within each other

• Leads to deeply nested code which is hard to read and maintain

• Can be avoided by using Promises or async/await syntax
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Q5. What is Async/Await ?
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Async/Await is a feature in JavaScript that allows for asynchronous programming using promises.
• Async/Await is syntactic sugar built on top of promises in JavaScript.

• It allows for writing asynchronous code that looks synchronous, making it easier to read and maintain.

• Async functions return a promise, which allows for chaining multiple asynchronous operations.

• Await keyword is used inside async functions to wait for a pro...read more
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Q1. Code A Todo List in React ?
Ans. 
A simple Todo List app built using React
• Create a new React project using create-react-app

• Create a Todo component to display the list of todos

• Use state to manage the list of todos and input field for adding new todos

• Implement functionality to add, delete, and mark todos as completed
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Q2. Difference Between RestApi and Graphql ?
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REST API is a standard protocol for web services using HTTP, while GraphQL is a query language for APIs.
• REST API follows a client-server architecture with stateless communication, while GraphQL allows clients to request only the data they need.

• REST API typically uses multiple endpoints for different resources, while GraphQL uses a single endpoint for flexible data retrieval.

• REST API has predefined data structures, whil...read more
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Q1. Reverse a list of strings [both string and list]
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Reversing a list of strings involves changing the order of elements and the characters within each string.
• To reverse a list, you can use slicing in Python: `reversed_list = original_list[::-1]`.

• To reverse each string in the list, use a list comprehension: `reversed_strings = [s[::-1] for s in original_list]`.

• Example: For `['apple', 'banana', 'cherry']`, reversing gives `['cherry', 'banana', 'apple']` and reversing stri...read more
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Q2. Prime number program
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A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers.
• A prime number has exactly two distinct positive divisors: 1 and itself.

• Examples of prime numbers include 2, 3, 5, 7, 11, and 13.

• The number 1 is not prime because it has only one positive divisor.

• The number 2 is the only even prime number; all other even numbers can be divided by 2.
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