Cognizant Full Stack Interview Questions and Answers

1. What are the benefits of server-side rendering (SSR)?

Advantages of server-side rendering

Improving initial page load performance, SEO,
Accessibility by providing faster time-to-content,
Better support for crawlers and screen readers.

2. How does Global Interpreter Lock (GIL) in Python impact multi-threaded programs?

In a multi-threaded environment, The Global Interpreter Lock allows execution of Python code at a time with only one thread. It limits the performance gains from multi-threading in CPU-bound applications. However, it does not affect I/O-bound or asynchronous I/O operations.

3. How metaclasses are used in Python?

Metaclasses are used for class validation, modification, and customization. They can be defined by subclassing type or by using the __metaclass__ attribute.

4. What is the difference between synchronous and asynchronous programming?

Synchronous programming executes tasks sequentially, blocking the execution until the current task completes. Asynchronous programming allows tasks to run concurrently, enabling non-blocking execution.

5. What are the SOLID principles in software development?

SOLID principles:

Single Responsibility,
Open/Closed,
Liskov Substitution,
Interface Segregation,
Dependency Inversion.

Set of design principles for making software designs more understandable, flexible, and maintainable:

6. How do you center a div horizontally and vertically in CSS?

Using Flexbox:

.container { display: flex; justify-content: center; align-items: center; height: 100vh; }

Using Grid:

.container { display: grid; place-items: center; height: 100vh; }

7. What is indexing in a database and why is it used?

Indexing improves the speed of data retrieval operations on a database table at the cost of additional storage and slower write operations.

8. How do you perform error handling in an Express.js application?

Using middleware to catch and handle errors:

app.use((err, req, res, next) => { res.status(500).send({ error: err.message }); });

9. What are Angular services?

Angular services are singleton objects that are instantiated once and shared throughout an application. They encapsulate reusable logic, data and functionality. It can be shared across multiple components.

10. What are the key differences between React context and prop drilling?

React context provides a way to pass data through the component tree without having to pass props manually at every level.

Prop drilling involves passing props down through multiple levels of nested components. It can lead to code clutter and reduced maintainability.

11. What is the purpose of the async and await keywords?

Async makes a function return a promise. await is used to wait for a promise to resolve.

12. What is hoisting in JavaScript?

Hoisting is JavaScript’s default behavior of moving declarations to the top of the current scope.

13. Explain call, apply, and bind.

Call and apply invoke a function with a specified ‘this’ value and arguments. Bind creates a new function with a specified ‘this’ value and initial arguments.

14. What is the difference between ArrayList and LinkedList in Java?

ArrayList uses a dynamic array to store elements and is faster for random access, while LinkedList uses a doubly linked list to store elements and is faster for insertion and deletion.

15. What is a try-with-resources statement in Java?

A try-with-resources statement ensures that each resource is closed at the end of the statement, reducing the boilerplate code for resource management.

16. What is Spring Security?

Spring Security is a powerful and highly customizable authentication and access-control framework for Java applications.

17. Explain the concept of lifting state up in React.

Lifting state up is a pattern in React which is used to manage state that needs to be shared between multiple components.

When two or more components need to reflect the same changing data, the state should be moved to their closest common ancestor. This ensures that the state is centralized and can be easily passed down as props to the relevant components.

18. What is the Stream API in Java?

The Stream API allows for functional-style operations on streams of elements, such as filtering, mapping, and reducing, enhancing the manipulation of collections.

19. What are promises?

Promises represent the eventual completion of an asynchronous operation and its resulting value.

20. What is an IIFE (Immediately Invoked Function Expression)?

An IIFE is a function that runs as soon as it is defined.

Syntax:

(function() { /* code */ })();

21. What is GraphQL?

GraphQL is a query language for APIs. It is a runtime for executing the queries by using a type system that you define for your data.

22. What tools or libraries can you use for asynchronous communication between React frontend and Spring Boot backend?

WebSockets: Socket.IO, Spring WebSocket
Server-Sent Events (SSE): EventSource API, Spring MVC SSE Support
Messaging Queues: RabbitMQ, Apache Kafka
RESTful APIs with Polling: Axios or Fetch API,Spring MVC REST Controllers.
GraphQL Subscriptions: Apollo Client, GraphQL.

23. What are template literals?

Template literals are string literals allowing embedded expressions.

Syntax: `string text ${expression} string text`.

24. What is the difference between map(), forEach(), and filter()?

map() creates a new array with results of calling a function on every element.

forEach() executes a function on each element.

filter() creates a new array with elements that pass a test.

25. What is the difference between StringBuilder and StringBuffer in Java?

StringBuilder is not synchronized and is faster, whereas StringBuffer is synchronized and thread-safe.

Request more information

Cognizant Full Stack Interview Questions and Answers