Persistent Systems Senior Software Engineer Interview Questions, Process, and Tips

Normal aptitude question in campus recruitment drive

Q1. Binary search algorithm explanation
Ans. 
Binary search is a divide and conquer algorithm that efficiently finds the target value in a sorted array.
• Divide the array in half and compare the target value with the middle element

• If the target value is smaller, search the left half. If larger, search the right half

• Repeat the process until the target value is found or the subarray is empty
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Q2. SQL Queries using JOINS
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SQL queries using JOINs are used to combine rows from two or more tables based on a related column between them.
• Use INNER JOIN to return rows when there is at least one match in both tables.

• Use LEFT JOIN to return all rows from the left table and the matched rows from the right table.

• Use RIGHT JOIN to return all rows from the right table and the matched rows from the left table.

• Use FULL JOIN to return rows when there i...read more
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Q1. Abhi yaad nahi, bahut time hua
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Q1. Tell us about yourself
Ans. 
I am a Senior Software Engineer with 8 years of experience in developing scalable web applications using Java, Spring Boot, and Angular.
• 8 years of experience in software development

• Skilled in Java, Spring Boot, and Angular

• Experience in developing scalable web applications
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Q1. Basic questions on Javascript
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Q2. Basic questions on angular
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Q1. What is Difference between let var const,
Ans. 
let, var, and const are all used to declare variables in JavaScript, but they have different scoping rules and behaviors.
• let and const were introduced in ES6, while var has been around since the beginning of JavaScript.

• let and const are block-scoped, while var is function-scoped.

• Variables declared with const cannot be reassigned, while let and var can be.

• const variables must be initialized when they are declared, while...read more
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Q2. Sql and Mongo related questions such as fetch 3rd highest salary from employee table?
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Q3. What are the scope in javascript, describe each one.
Ans. 
Scopes in JavaScript determine the accessibility of variables and functions.
• Global scope: variables and functions declared outside any function are accessible globally

• Local scope: variables and functions declared inside a function are only accessible within that function

• Block scope: variables declared with let and const are only accessible within the block they are declared in

• Function scope: variables declared with var...read more
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Q4. What is callback hell, what is Promises?
Ans. 
Callback hell is a situation where nested callbacks make code unreadable. Promises are a solution to this problem.
• Callback hell occurs when there are too many nested callbacks in asynchronous code

• It makes the code difficult to read and maintain

• Promises are a way to handle asynchronous operations without nested callbacks

• Promises can be used to chain multiple asynchronous operations together

• Promises have a resolve and re...read more
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Q5. What is express js and why it is used in web apps and what is body parser
Ans. 
Express.js is a popular Node.js web framework used for building web applications. Body-parser is a middleware used to parse incoming request bodies.
• Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

• It provides a way to handle HTTP requests and responses, routing, middleware, and more.

• Body-parser is a middleware used to parse inc...read more
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Q6. What are arrow functions
Ans. 
Arrow functions are a concise way to write functions in JavaScript.
• They have a shorter syntax than traditional function expressions.

• They do not have their own 'this' keyword.

• They are not suitable for methods, constructors, or prototype methods.

• Example: const add = (a, b) => a + b;

• Example: const square = x => x * x;
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Q7. What is nodejs and difference between nodejs and javascript
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Node.js is a server-side JavaScript runtime environment.
• Node.js is built on top of the V8 JavaScript engine from Google Chrome.

• It allows developers to write server-side code in JavaScript.

• Node.js has a non-blocking I/O model, making it efficient for handling large amounts of data.

• Node.js has a vast library of modules available through npm (Node Package Manager).
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Q8. What is passport.js why it is used
Ans. 
Passport.js is an authentication middleware for Node.js.
• Passport.js provides a simple way to authenticate users with various authentication strategies such as local, OAuth, OpenID, etc.

• It is highly customizable and can be integrated with any Node.js web application framework.

• Passport.js maintains user sessions and provides a consistent API for authentication across different strategies.

• Example: Using Passport.js with E...read more
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Q9. Difference between node and expressjs
Ans. 
Node is a runtime environment for executing JavaScript code, while Express is a web application framework built on top of Node.
• Node provides the platform for running JavaScript code outside of a web browser

• Express is a lightweight framework that simplifies building web applications on top of Node

• Express provides features like routing, middleware, and templating that make it easier to build web applications

• Node and Expr...read more
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Q10. Why nodejs is single Threaded
Ans. 
Node.js is single-threaded to optimize performance and simplify programming.
• Node.js uses an event-driven, non-blocking I/O model.

• This allows for efficient handling of multiple requests without creating new threads.

• Node.js also uses a single event loop to manage all I/O operations.

• This simplifies programming by eliminating the need for complex thread synchronization.

• However, Node.js can still take advantage of multi-cor
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Q1. A small data structures problem was given to solve
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Q2. A small web api asked to build which includes crud operations
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Q3. Question related to system design
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Q4. What is Function hoisting
Ans. 
Function hoisting is a JavaScript behavior where function declarations are moved to the top of their scope.
• Function declarations are moved to the top of their scope during the compilation phase.

• Function expressions are not hoisted.

• Hoisting can lead to unexpected behavior and bugs if not understood properly.
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Q5. What is event loops and phases
Ans. 
Event loop is a mechanism that allows JavaScript to perform non-blocking I/O operations.
• Event loop is a loop that constantly checks the message queue and executes the next message if there is any.

• Phases are the different stages of the event loop, such as timers, I/O callbacks, idle, and poll.

• Event loop is crucial for Node.js to handle multiple requests simultaneously without blocking the main thread.

• Example: setTimeout...read more
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Q1. Normal technical discussion on Java, SQL, spring,spring boot, rest services
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Java 8 complex poblems

Q1. List manipulation using list comprehension and lambda function for prime number
Ans. 
Using list comprehension and lambda function to manipulate a list of prime numbers
• Use list comprehension to generate a list of numbers

• Use a lambda function to check if a number is prime

• Filter the list of numbers using the lambda function to get prime numbers
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Q2. Move all the zeros at last
Ans. 
Move all zeros in an array to the end while maintaining the order of other elements.
• Iterate through the array and move all zeros to the end while keeping the order of non-zero elements.

• Use two pointers approach to swap elements in-place.

• Example: Input [0, 1, 0, 3, 12], Output [1, 3, 12, 0, 0]
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Q1. About project and design patterns
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Q2. SQL query for 2nd highest salary
Ans. 
SQL query to find the 2nd highest salary in a table
• Use the ORDER BY clause to sort the salaries in descending order

• Use the LIMIT clause to limit the result to the second row

• Consider handling cases where there might be ties for the highest salary
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General Details were asked

Common coding questions are there

Q1. Compensation expectation
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Q2. Terms & conditions
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