The document provides an overview of various web development topics, including HTML/CSS, JavaScript, front-end frameworks, back-end languages, databases, HTTP & REST, web security, data structures, system design, and DevOps tools. It covers key concepts such as the purpose of doctype, the CSS box model, closures in JavaScript, REST architecture, SQL vs. NoSQL databases, and tools like Docker, Kubernetes, AWS, and Git. Each concept is explained with a brief definition or description, making it a concise reference for web developers.

1. HTML/CSS
1. What is the purpose of Doctype in HTML?
○ Doctype stands for Document Type Declaration. It informs the web
browser about the version of HTML that the page is written in.
2. Explain the CSS box model.
○ The CSS box model is a rectangular layout paradigm for HTML elements
that consists of the following: content, padding, border, and margin.
3. What is the difference between id and class in CSS?
○ id is unique to each element and each element can have only one id, while
class can be used to identify multiple elements.
4. How do you make a website responsive?
○ Responsive design can be achieved through flexible grid layouts, flexible
images/media, and media queries.
JavaScript 5. What is a closure in JavaScript?
● A closure is a function that has access to its own scope, the outer function’s
scope, and the global scope.
6. What is the difference between == and === in JavaScript?
○ == checks for equality with type coercion, while === checks for equality
without type coercion, i.e., it checks for both value and type.
7. What is the use of bind method in JavaScript?
○ The bind method creates a new function that, when called, has its this
keyword set to the provided value.
8. Explain how this keyword works in JavaScript.
○ this keyword refers to an object that’s set at the creation of a new
execution context (function invocation).
Frontend Frameworks 9. What is the virtual DOM in React?
● The virtual DOM is a programming concept where an ideal, or “virtual”,
representation of a UI is kept in memory and synced with the “real” DOM.
10.What is a directive in Angular?
● Directives are markers on a DOM element that tell Angular to attach a specified
behavior to that DOM element or even transform the DOM element and its
children.
Backend Language 11. What is Node.js?

2. ● Node.js is a platform built on Chrome’s JavaScript runtime for easily building fast
and scalable network applications.
12.What is Express.js?
● Express.js is a minimal and flexible Node.js web application framework that
provides a robust set of features for web and mobile applications.
Databases 13. What is the difference between SQL and NoSQL databases?
● SQL databases are relational, NoSQL are non-relational. SQL databases use
structured query language and have a predefined schema. NoSQL databases
have dynamic schemas for unstructured data.
14.What are ACID properties in databases?
● ACID stands for Atomicity, Consistency, Isolation, Durability. These are a set of
properties that guarantee that database transactions are processed reliably.
HTTP & REST 15. What is the difference between GET and POST methods in HTTP?
● GET is used to request data from a specified resource, POST is used to send data
to a server to create/update a resource.
16.What is REST?
● REST stands for Representational State Transfer. It is an architectural style for
distributed hypermedia systems and was first presented by Roy Fielding in 2000
in his famous dissertation.
Web Security 17. What is Cross-Site Scripting (XSS)?
● Cross-Site Scripting (XSS) attacks are a type of injection, in which malicious
scripts are injected into otherwise benign and trusted websites.
18.What is Cross-Site Request Forgery (CSRF)?
● CSRF is an attack that tricks the victim into submitting a malicious request. It
uses the identity and privileges of the victim to perform an undesired function on
their behalf.
Data Structures and Algorithms 19. What is a linked list?
● A linked list is a linear data structure where each element is a separate object.
Each element (node) of a list consists of two items - the data and a reference to
the next node.
20.What is the time complexity of binary search?
● The time complexity of binary search is O(log n).
System Design 21. What is microservices architecture?

3. ● Microservices - also known as the microservice architecture - is an architectural
style that structures an application as a collection of services that are highly
maintainable and testable, loosely coupled, independently deployable, organized
around business capabilities, and owned by a small team.
22.What is a load balancer?
● A load balancer is a device that acts as a reverse proxy and distributes network
or application traffic across a number of servers.
DevOps 23. What is CI/CD?
● CI/CD stands for Continuous Integration/Continuous Deployment. It is a method
to frequently deliver apps to customers by introducing automation into the
stages of app development.
24.What is Docker?
● Docker is an open platform for developing, shipping, and running applications.
Docker enables you to separate your applications from your infrastructure so you
can deliver software quickly.
25.What is Kubernetes?
● Kubernetes, also known as K8s, is an open-source system for automating
deployment, scaling, and management of containerized applications.
Frontend Frameworks 26. What is Redux in React?
● Redux is a predictable state container for JavaScript apps. It helps you write
applications that behave consistently, run in different environments (client, server,
and native), and are easy to test.
27.What is Vue.js?
● Vue.js is a progressive JavaScript framework for building user interfaces. Unlike
other monolithic frameworks, Vue is designed from the ground up to be
incrementally adoptable.
Backend Language 28. What is Django?
● Django is a high-level Python web framework that encourages rapid development
and clean, pragmatic design.
29.What is Flask?
● Flask is a micro web framework written in Python. It is classified as a
microframework because it does not require particular tools or libraries.
Databases 30. What is MongoDB?

4. ● MongoDB is a source-available cross-platform document-oriented database
program. Classified as a NoSQL database program, MongoDB uses JSON-like
documents with optional schemas.
31.What is PostgreSQL?
● PostgreSQL, also known as Postgres, is a free and open-source relational
database management system emphasizing extensibility and SQL compliance.
HTTP & REST 32. What is GraphQL?
● GraphQL is an open-source data query and manipulation language for APIs, and a
runtime for executing those queries with your existing data.
33.What is SOAP?
● SOAP (Simple Object Access Protocol) is a messaging protocol that allows
programs that run on disparate operating systems to communicate with each
other.
Web Security 34. What is a JWT?
● JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact
and self-contained way for securely transmitting information between parties as
a JSON object.
35.What is HTTPS?
● HTTPS is an extension of the Hypertext Transfer Protocol (HTTP). It is used for
secure communication over a computer network, and is widely used on the
Internet.
Data Structures and Algorithms 36. What is a binary tree?
● A binary tree is a tree data structure in which each node has at most two children,
which are referred to as the left child and the right child.
37.What is a hash table?
● A hash table, also known as a hash map, is a data structure that implements an
associative array abstract data type, a structure that can map keys to values.
System Design 38. What is a CDN?
● A content delivery network, or content distribution network (CDN), is a
geographically distributed network of proxy servers and their data centers.
39.What is caching?
● Caching is the process of storing copies of files in a cache, or temporary storage
location, so that they can be accessed more quickly.
DevOps 40. What is AWS?

5. ● Amazon Web Services (AWS) is a subsidiary of Amazon providing on-demand
cloud computing platforms and APIs to individuals, companies, and
governments, on a metered pay-as-you-go basis.
41.What is Azure?
● Microsoft Azure, commonly referred to as Azure, is a cloud computing service
created by Microsoft for building, testing, deploying, and managing applications
and services through Microsoft-managed data centers.
42.What is GCP?
● Google Cloud Platform (GCP), offered by Google, is a suite of cloud computing
services that runs on the same infrastructure that Google uses internally for its
end-user products, such as Google Search, Gmail, file storage, and YouTube.
43.What is Jenkins?
● Jenkins is an open source automation server. It helps automate the parts of
software development related to building, testing, and deploying, facilitating
continuous integration and continuous delivery.
44.What is Git?
● Git is a free and open source distributed version control system designed to
handle everything from small to very large projects with speed and efficiency.
45.What is Docker Compose?
● Docker Compose is a tool for defining and running multi-container Docker
applications. With Compose, you use a YAML file to configure your application’s
services.
46.What is Kubernetes?
● Kubernetes, also known as K8s, is an open-source system for automating
deployment, scaling, and management of containerized applications.
47.What is Terraform?
● Terraform is an open-source infrastructure as code software tool that provides a
consistent CLI workflow to manage hundreds of cloud services.
48.What is Ansible?
● Ansible is an open-source software provisioning, configuration management, and
application-deployment tool enabling infrastructure as code.
49.What is Nagios?
● Nagios is a free and open source computer-software application that monitors
systems, networks and infrastructure.
50.What is ELK Stack?
● ELK Stack is a collection of three open-source products — Elasticsearch,
Logstash, and Kibana. They are all developed, managed ,and maintained by the
company Elastic.
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