40+ Senior Full Stack Developer Interview Questions and Answers

Clients of one domain can access API service through authentication and authorization managed by API service.

• API service can use OAuth2.0 for authentication and authorization

• Different domains can have different client IDs and secrets for OAuth2.0

• API service can use JWT for token-based authentication

• Cross-Origin Resource Sharing (CORS) can be used to allow access from different domains

Authentication system in API service must be configured securely to prevent external hacking.

• Use strong encryption algorithms to store passwords

• Implement multi-factor authentication

• Use HTTPS protocol to encrypt data in transit

• Implement rate limiting to prevent brute force attacks

• Regularly update and patch the authentication system

• Use secure coding practices to prevent injection attacks

In critical situations, I prioritize communication, analysis, and collaboration to effectively resolve issues.

• Assess the situation quickly: Gather all relevant information to understand the problem.

• Communicate with the team: Ensure everyone is aware of the issue and their roles in resolving it.

• Prioritize tasks: Identify the most critical aspects that need immediate attention.

• Implement a solution: Use a collaborative approach to develop and execute a plan.

• Review and learn: Aft...read more

Implementing caching mechanisms has significantly increased performance and improved delivery times.

• Utilizing caching mechanisms such as Redis or Memcached to store frequently accessed data

• Implementing CDN (Content Delivery Network) to cache static assets and reduce server load

• Optimizing database queries and indexing to improve retrieval speed

• Implementing lazy loading for images and resources to reduce initial load times

Service provides data and functionality while Component handles UI and user interaction.

• Service is a singleton object that can be injected into multiple components

• Component is a directive with a template and styles

• Service provides data and functionality to components

• Component handles UI and user interaction

• Services can be used to share data between components

• Components can communicate with services using dependency injection

I prepared the design doc by outlining the requirements, architecture, data flow, and user interactions.

• Outlined the requirements and goals of the feature

• Defined the architecture and technologies to be used

• Described the data flow and interactions between components

• Included wireframes or mockups for user interfaces

• Listed potential edge cases and how to handle them

Design a parking system with APIs for managing parking spots and reservations.

• Create API for adding new parking spots with details like location, availability, and pricing

• Create API for listing available parking spots based on location and availability

• Create API for reserving a parking spot with user details and duration

• Create API for cancelling a parking reservation

• Response object for adding parking spot: { success: true, message: 'Parking spot added successfully' }

• Response ...read more

Developed a real-time chat feature for a social networking platform.

• Implemented WebSocket technology for instant messaging

• Designed user interface for chat window with message history

• Integrated push notifications for new messages

• Developed backend logic for message encryption and decryption

Design a system for transferring images and documents to clients.

• Use a secure file transfer protocol like SFTP or HTTPS

• Implement a user-friendly interface for clients to upload and download files

• Utilize cloud storage for scalability and accessibility

• Include encryption for data security

• Implement version control for tracking changes

I prioritize communication, quick assessment, and systematic troubleshooting during production deployment issues.

• Maintain clear communication with the team and stakeholders to keep everyone informed about the situation.

• Quickly assess the impact of the issue to determine if a rollback is necessary, as in a case where a new feature causes a critical failure.

• Implement logging and monitoring tools to identify the root cause of the problem, such as using Sentry for error tracking....read more

I solve complex production environments by identifying issues, optimizing performance, and implementing solutions.

• Identifying bottlenecks and optimizing performance

• Troubleshooting and resolving production issues

• Implementing scalable solutions for high traffic websites

• Working with cloud services like AWS or Azure

• Automating deployment processes with tools like Jenkins or Docker

Closures, callbacks, promises, and async/await are JavaScript concepts for handling asynchronous operations and scope.

• Closure: A function that retains access to its lexical scope even when the function is executed outside that scope. Example: `function outer() { let x = 10; return function inner() { return x; }; }`

• Callback: A function passed as an argument to another function, executed after a certain event or operation. Example: `setTimeout(() => console.log('Hello'), 1000);...read more

Microservices communicate through APIs to exchange data and perform actions.

• Microservices are independent and self-contained

• Each microservice has its own API

• APIs are used to communicate between microservices

• Data is exchanged through APIs

• Microservices can perform actions based on data received from other microservices

System design in Node.js involves applying SOLID principles and design patterns for scalable and maintainable applications.

• Use SOLID principles (Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion) to design modular and flexible systems.

• Apply design patterns like MVC, Factory, Singleton, Observer, etc. to address common design problems and improve code reusability.

• Utilize Node.js features like event-driven architecture, non-blo...read more

Breadcrumbs in React can be built using a combination of state management and conditional rendering.

• Create a state variable to store the breadcrumb data.

• Update the state variable as the user navigates through the application.

• Render the breadcrumbs component with the data stored in the state.

Implementing SEO enhances online visibility, driving organic traffic and improving user experience on websites.

• Increased Visibility: Higher search engine rankings lead to more visibility. For example, a local bakery optimizing for 'best cupcakes' can attract more customers.

• Organic Traffic: SEO helps in attracting visitors without paid ads. A blog on healthy recipes can gain traffic through relevant keywords.

• User Experience: SEO practices improve site structure and navigation,...read more

A schema defines the structure, organization, and constraints of data in a database.

• A schema includes tables, fields, data types, and relationships between tables.

• For example, in a 'Users' table, fields might include 'UserID', 'Username', and 'Email'.

• Schemas can enforce rules, such as unique constraints on 'Username' to prevent duplicates.

• In relational databases, schemas help maintain data integrity and facilitate queries.

The Event Loop in Node.js manages asynchronous operations, allowing non-blocking execution of code.

• Node.js operates on a single-threaded event loop, enabling it to handle multiple connections concurrently.

• The event loop processes events and executes callbacks, ensuring efficient use of resources.

• It consists of phases: timers, I/O callbacks, idle, poll, check, and close callbacks.

• Example: When a file read operation is initiated, Node.js continues executing other code while wai...read more

You can host a local WordPress site using tools like XAMPP, MAMP, or Local by Flywheel.

• Install a local server environment like XAMPP or MAMP.

• Download WordPress from wordpress.org.

• Place the WordPress files in the server's 'htdocs' or 'www' directory.

• Create a MySQL database using phpMyAdmin.

• Configure 'wp-config.php' with database details.

• Access the site via 'localhost' in your web browser.

To call a REST API in Angular, use the HttpClient module to make HTTP requests.

• Import HttpClientModule in app.module.ts

• Inject HttpClient in the component/service where API call needs to be made

• Use HttpClient methods like get(), post(), put(), delete() to make API calls

• Subscribe to the Observable returned by HttpClient methods to get the response data

• Handle errors using catchError() method

To find the first non-repeating character in a string, we can use a frequency count and then identify the first unique character.

• Use a hash map to count occurrences of each character.

• Iterate through the string a second time to find the first character with a count of 1.

• Example: In 'swiss', 'w' is the first unique character.

• Example: In 'racecar', 'e' is the first unique character.

useState in React is asynchronous, meaning state updates may not reflect immediately after calling setState.

• useState updates are batched for performance, leading to asynchronous behavior.

• Example: Calling setCount(count + 1) multiple times in a loop may not yield expected results immediately.

• To see the updated state, use the useEffect hook or a callback function.

• React batches state updates in event handlers, making them appear synchronous.

I am very familiar with frontend development, with experience in various frameworks and technologies.

• Proficient in HTML, CSS, and JavaScript

• Experience with frontend frameworks like React, Angular, and Vue.js

• Knowledge of responsive design and cross-browser compatibility

• Familiarity with frontend build tools like Webpack and Babel

Check if Array2 is a substring of Array1

• Iterate through Array1 and check if each element contains Array2

• Use built-in string functions like includes() or indexOf() to check for substring

• Consider edge cases like empty arrays or arrays with empty strings

useMemo is a hook used for memoization in React to optimize performance, while Memo is a higher order component used for memoization.

• useMemo is a hook in React that memoizes a function and returns the memoized value.

• Memo is a higher order component in React that memoizes the component and prevents unnecessary re-renders.

• useMemo is typically used for memoizing expensive calculations or functions, while Memo is used for memoizing components.

• Example: useMemo(() => calculateValue...read more

I have experience with a variety of technologies including JavaScript, React, Node.js, MongoDB, and AWS.

• JavaScript

• React

• Node.js

• MongoDB

• AWS

Cookies are stored on the client side while tokens are stored on the server side for authentication purposes.

• Cookies are sent with every HTTP request, while tokens are typically sent in the Authorization header.

• Cookies can be vulnerable to CSRF attacks, while tokens can be more secure if implemented correctly.

• Cookies have a size limit of 4KB, while tokens can store more data.

• Cookies are typically used for session management, while tokens are commonly used for authentication i...read more