Full-stack developer (React/Node.js)

This role is ideal for a Senior Full-stack Developer with 4+ years of experience in React.js (preferably Next.js) and Node.js (Nest.js/Express), plus solid knowledge of HTML5, CSS3, TypeScript, and databases like MySQL, PostgreSQL, or MongoDB. You should be comfortable building scalable, secure web applications, integrating APIs, optimizing performance, and collaborating closely with designers and cross-functional teams. Experience with AWS/Azure/Google Cloud, Docker/Kubernetes, and CI/CD pipelines will be a strong advantage.

1. What are the main differences between React and Next.js, and when would you choose one over the other?
   React is a library for building UI components, while Next.js is a framework built on React that offers server-side rendering, static site generation, and routing out-of-the-box. Next.js is preferred for SEO-friendly, performance-optimized applications.

2. How do you manage state in a React application with complex data flows?
   State can be managed using React’s built-in useState and useReducer hooks, Context API for global state, or external libraries like Redux or Zustand for more complex cases.

3. Explain how you would structure a RESTful API in Node.js using Express.
   Organize routes by resource, separate concerns with controllers and services, use middleware for authentication, validation, and error handling, and ensure proper HTTP status codes are returned.

4. How would you implement authentication in a full-stack React/Node.js application?
   Use JWT for stateless authentication or sessions with cookies, handle login/registration on the backend, store tokens securely, and protect routes both on client and server.

5. What are some ways to optimize a React application for performance?
   Use memoization (React.memo, useMemo, useCallback), code splitting with dynamic imports, lazy loading, avoiding unnecessary re-renders, and minimizing bundle size.

6. How do you ensure the security of a Node.js application?
   Implement input validation, use parameterized queries to prevent SQL injection, sanitize user input, handle authentication properly, use HTTPS, and manage environment variables securely.

7. Describe how you would design a database schema for a user management system.
   Create a users table with fields for ID, name, email, password hash, roles, and timestamps, ensure email uniqueness, and index frequently queried fields.

8. What are the benefits of using TypeScript in a full-stack project?
   TypeScript provides static type checking, reduces runtime errors, improves code maintainability, and enhances developer productivity with better autocomplete and refactoring tools.

9. How would you set up CI/CD for a React/Node.js application?
   Use tools like GitHub Actions or GitLab CI, configure pipelines for build, test, lint, and deploy stages, and integrate with cloud platforms or Docker/Kubernetes for deployment.

10. What is the difference between SQL and NoSQL databases, and when would you choose each?
    SQL databases (e.g., MySQL, PostgreSQL) use structured schemas and are great for relational data. NoSQL databases (e.g., MongoDB, Redis) offer flexibility, scalability, and better performance for unstructured or rapidly changing data.

Join Diffco, a Silicon Valley–driven company, as a Full-stack Developer (React/Node.js) and work on cutting-edge projects with modern tech like Next.js, Nest.js, and cloud platforms (AWS, Azure, GCP). You’ll design, build, and optimize scalable web applications, collaborating with a talented and friendly team in a flexible, fully remote setup. We offer competitive pay, bonuses, and professional growth opportunities in an environment that values innovation, work-life balance, and continuous learning. This is your chance to work on impactful solutions while enjoying a vibrant, supportive culture.