1. What is microservices architecture, and how does it benefit Full Stack development?

Answer:
Microservices architecture is a software development approach where applications are built as a collection of small, loosely coupled services, each responsible for a specific function.
Benefits:

• Scalability: Independent services can be scaled individually.

• Flexibility: Different technologies can be used for different services.

• Fault isolation: If one service fails, the rest of the application remains functional.

• Faster deployment and updates.

2. How do you optimize the performance of a Full Stack application?

Answer:

• Frontend: Minimize HTTP requests, use lazy loading, and enable caching.

• Backend: Optimize database queries, implement indexing, and use load balancers.

• Database: Normalize tables, use indexing, and implement caching (e.g., Redis).

• Networking: Use CDN for assets, implement Gzip compression, and minimize API calls.

3. What is Server-Side Rendering (SSR) vs. Client-Side Rendering (CSR)?

Answer:

• SSR: The server processes the request and sends a fully rendered HTML page to the client. Improves SEO and initial load speed (e.g., Next.js).

• CSR: The client downloads a minimal HTML page and dynamically fetches content using JavaScript (React, Angular, Vue). It enhances interactivity but may affect SEO.

4. Explain the difference between SQL and NoSQL databases. When would you use each?

Answer:

• SQL Databases (MySQL, PostgreSQL, MSSQL)

  • Structured schema

  • Uses tables and relationships

  • ACID-compliant (Atomicity, Consistency, Isolation, Durability)

  • Best for applications with structured data (e.g., banking, CRM).

• NoSQL Databases (MongoDB, Cassandra, Firebase)

  • Schema-less, flexible structure

  • Uses key-value, document, or graph-based storage

  • Horizontal scalability

  • Ideal for unstructured or semi-structured data (e.g., social media, IoT).

5. What is WebSockets, and how is it used in real-time applications?

Answer:
WebSockets is a protocol that enables persistent, full-duplex communication between a client and a server over a single connection.

• Used in chat apps, stock market dashboards, multiplayer games, and live notifications.

• Implemented using Socket.io in Node.js or native WebSockets in browsers.

6. What are JWT tokens, and how do they work in authentication?

Answer:
JWT (JSON Web Token) is a compact, self-contained way of securely transmitting information between parties as a JSON object.

• Used for authentication in RESTful APIs.

• Contains three parts: Header, Payload, and Signature.

• The server generates and signs the JWT, and the client stores it (local storage, cookies).

• Each request includes the JWT token in the authorization header for verification.

7. How do you ensure security in a Full Stack application?

Answer:

• Use HTTPS to encrypt data in transit.

• Implement JWT or OAuth2 for authentication.

• Protect against SQL injection using parameterized queries.

• Use CORS to restrict cross-origin requests.

• Prevent CSRF (Cross-Site Request Forgery) using CSRF tokens.

• Hash passwords using bcrypt.

• Regular security updates for dependencies.

8. What is CI/CD, and how does it improve development workflows?

Answer:
CI/CD (Continuous Integration/Continuous Deployment) automates software development, testing, and deployment.

• CI (Continuous Integration): Automates code testing and integration into a shared repository (e.g., GitHub Actions, Jenkins).

• CD (Continuous Deployment): Automates pushing changes to production (e.g., Docker, Kubernetes, AWS CodeDeploy).

9. How does Docker help in Full Stack development?

Answer:
Docker provides lightweight, portable containers that package an application with its dependencies.

• Ensures consistency across development, testing, and production environments.

• Reduces dependency conflicts (e.g., different Node.js versions).

• Improves scalability with container orchestration (Kubernetes).

10. What are GraphQL and REST APIs, and when would you use each?

Answer:

• REST API:

  • Uses HTTP methods (GET, POST, PUT, DELETE).

  • Fixed data structure with multiple endpoints.

  • Suitable for simpler applications with predictable queries.

• GraphQL API:

  • Clients request only the data they need, reducing over-fetching.

  • Uses a single endpoint with flexible queries.

  • Best for complex applications with diverse data needs (e.g., social media apps)

11. What is GraphQL and how does it differ from REST?

Answer:
GraphQL is a query language for APIs that allows clients to request exactly the data they need.

• GraphQL: Single endpoint, query-based, returns only requested fields.

• REST: Multiple endpoints, fixed data structures, may over-fetch or under-fetch data.

12. Explain the concept of containerization and its benefit in full stack development.

Answer:
Containerization (e.g., using Docker) involves packaging applications and their dependencies into isolated environments.
Benefits:

• Consistent across environments

• Easier deployment and scaling

• Resource-efficient compared to VMs

13. What is Serverless Architecture?

Answer:
Serverless computing allows developers to build and run applications without managing servers.
Cloud providers handle infrastructure, scaling, and maintenance (e.g., AWS Lambda, Azure Functions).

14. What are Micro Frontends?

Answer:
Micro frontends break a frontend application into smaller, independent pieces managed by separate teams, similar to microservices in the backend.
Used for scalability and modularity.

15. How does OAuth 2.0 work in a full stack application?

Answer:
OAuth 2.0 is an authorization framework. A client app redirects the user to an authorization server, gets an access token, and uses it to access protected resources from a resource server.

16. How can you implement caching in full stack apps?

Answer:

• Frontend: LocalStorage, SessionStorage, Service Workers

• Backend: In-memory caching (e.g., Redis, Memcached), HTTP caching headers, CDN caching for static assets

17. What is the CAP theorem in database systems?

Answer:
CAP stands for Consistency, Availability, and Partition Tolerance. A distributed system can only guarantee two out of these three properties.

18. What is the difference between SSR, CSR, and SSG?

Answer:

• SSR (Server-Side Rendering): Content is rendered on the server at request time.

• CSR (Client-Side Rendering): Content rendered in the browser via JavaScript.

• SSG (Static Site Generation): HTML is pre-built at build time (e.g., Next.js, Gatsby).

19. How do you ensure scalability in a full stack application?

Answer:

• Load balancing

• Horizontal scaling (replicate services)

• Use microservices

• Caching and CDN

• Database sharding and replication

20. How does Kubernetes help in full stack deployments?

Answer:
Kubernetes automates deployment, scaling, and management of containerized apps.
It manages clusters of Docker containers with features like load balancing, service discovery, auto-scaling, and self-healing.

21. What are Webhooks and when are they used?

Answer:
Webhooks are automated HTTP callbacks triggered by events. Common in integrations (e.g., Stripe, GitHub) to notify external services when something happens.

22. How do you implement CI/CD in a full stack project?

Answer:
Using tools like Jenkins, GitHub Actions, GitLab CI, or CircleCI to automate:

• Code testing

• Building

• Deployment to staging/production
  Integrates version control, testing, and deployment pipelines.

23. How does Domain-Driven Design (DDD) influence full stack architecture?

Answer:
DDD emphasizes designing software based on the business domain.
It encourages modularity, aligning code structure with business processes, and using bounded contexts for complex systems.

24. What are the benefits of using TypeScript in full stack development?

Answer:

• Static typing and type safety

• Better IDE support and autocomplete

• Easier refactoring and debugging

• Works on both frontend (React, Angular) and backend (Node.js)

25. What are some strategies to prevent SQL injection attacks?

Answer:

• Use prepared statements or ORM

• Validate and sanitize user input

• Avoid dynamic SQL

• Use web application firewalls (WAF)

• Apply least privilege principle on DB access

1. What is the difference between SQL and NoSQL databases?

Answer:

• SQL (Relational): Structured data, tables, uses SQL (e.g., MySQL, PostgreSQL).

• NoSQL (Non-relational): Flexible schema, document/key-value/store-based (e.g., MongoDB, Redis).

2. What is RESTful API and how does it work?

Answer:
A RESTful API uses HTTP methods (GET, POST, PUT, DELETE) to perform CRUD operations on resources identified by URIs.

3. What is middleware in Express.js?

Answer:
Middleware functions in Express.js are functions that execute during the lifecycle of a request to the server. They can modify request/response and control request flow.

4. Explain the difference between authentication and authorization.

Answer:

• Authentication: Verifies identity (e.g., login).

• Authorization: Grants permissions based on roles or policies (e.g., access to admin dashboard).

5. What is a closure in JavaScript?

Answer:
A closure is a function that has access to variables from its outer scope, even after the outer function has returned.

6. What is the role of Webpack in a web application?

Answer:
Webpack is a module bundler that compiles JavaScript files, CSS, and assets into optimized bundles for efficient browser usage.

7. What are Promises and async/await in JavaScript?

Answer:

• Promises: Handle asynchronous operations using .then() and .catch().

• async/await: Syntax sugar over Promises for more readable async code.

8. What is the virtual DOM in React?

Answer:
The virtual DOM is an in-memory representation of the actual DOM. React updates the virtual DOM first and then updates the real DOM efficiently using diffing.

9. What are hooks in React?

Answer:
Hooks are functions (like useState, useEffect) that let you use state and lifecycle features in functional components.

10. What is CORS and how do you handle it?

Answer:
CORS (Cross-Origin Resource Sharing): A browser security feature restricting cross-origin requests.
Handled by setting appropriate headers (like Access-Control-Allow-Origin) on the server.

11. What is the difference between monolithic and microservices architecture?

Answer:

• Monolithic: One large codebase for all functionalities.

• Microservices: Breaks the app into smaller, independent services that communicate over APIs.

12. What are web sockets and where are they used?

Answer:
WebSockets provide full-duplex communication channels over a single TCP connection. Used in real-time apps like chats, games, and notifications.

13. How do you handle file uploads in a full stack app?

Answer:
Use FormData on frontend and middleware like multer in Node.js or IFormFile in .NET on backend to receive and process files.

14. What is JWT and how is it used?

Answer:
JWT (JSON Web Token): A compact, secure token used for authentication and data transmission. Sent in headers to verify users.

15. How do you secure passwords in full stack apps?

Answer:
Use strong hashing algorithms like bcrypt or argon2, salt the hashes, and never store plain-text passwords.

16. How do you implement pagination on the frontend and backend?

Answer:

• Backend: Limit and offset/skip queries.

• Frontend: Handle next/previous buttons or infinite scrolling using pagination metadata.

17. What is the difference between GET and POST methods?

Answer:

• GET: Retrieves data; parameters in URL.

• POST: Sends data to the server; parameters in the body, more secure for sensitive data.

18. What are environment variables and why are they important?

Answer:
Used to store config like API keys and DB URLs separately from code. Prevents hardcoding sensitive data.

19. How do you handle error logging in production?

Answer:
Use tools like Winston, Log4Net, Sentry, or ELK Stack to log and monitor errors and exceptions.

20. What is the role of an ORM in full stack development?

Answer:
ORM (Object-Relational Mapping) maps database tables to objects.
Examples: Sequelize (Node.js), Entity Framework (.NET), Hibernate (Java), Django ORM (Python).

21. How do you optimize the performance of a React app?

Answer:

• Code splitting with dynamic import

• Memoization (React.memo, useMemo)

• Avoid unnecessary re-renders

• Lazy loading components

22. What is state management and what tools are used?

Answer:
State management handles data across components. Tools include Redux, Zustand, MobX, and Context API.

23. What is the difference between SQL joins: INNER, LEFT, RIGHT, FULL?

Answer:

• INNER JOIN: Matches in both tables

• LEFT JOIN: All from left + matches

• RIGHT JOIN: All from right + matches

• FULL JOIN: All records with or without matches

24. How do you protect against CSRF attacks?

Answer:

• Use CSRF tokens

• Use SameSite cookie attributes

• Validate origin headers

25. What is a CDN and how does it help?

Answer:
CDN (Content Delivery Network) caches and serves static assets from locations closer to the user to reduce load time and improve performance.

Let me know if you want these in a document or want me to continue with more advanced or domain-specific sets.