Key questions to ask when evaluating Node.js developers, from fundamental concepts to advanced patterns.
Evaluating Node.js Talent
Hiring the right Node.js developers is crucial for your project's success. These interview questions will help you assess candidates' knowledge and problem-solving abilities.
Fundamental Questions
Understanding of Node.js Core
Q: Explain the Node.js event loop and why it matters.
*What to look for:* Understanding of single-threaded, non-blocking I/O model. Candidates should explain phases (timers, pending callbacks, idle/prepare, poll, check, close callbacks) and why this architecture suits I/O-heavy applications.
Q: What is the difference between process.nextTick() and setImmediate()?
*What to look for:* Knowledge of the event loop phases. process.nextTick() executes before the next event loop iteration; setImmediate() executes in the check phase.
Q: How does Node.js handle child processes?
*What to look for:* Understanding of spawn, fork, exec, and execFile methods and when to use each.
Intermediate Questions
Asynchronous Programming
Q: Compare callbacks, Promises, and async/await. When would you use each?
*What to look for:* Understanding that async/await is syntactic sugar over Promises, which are abstractions over callbacks. Practical knowledge of when each pattern is appropriate.
Q: How do you handle errors in async functions?
*What to look for:* Knowledge of try/catch with async/await, .catch() with Promises, and error-first callbacks. Understanding of unhandled rejection handling.
API Development
Q: How would you structure a large Express.js application?
*What to look for:* Understanding of modular architecture, middleware patterns, route organization, and separation of concerns.
Q: Explain middleware in Express and give examples of custom middleware you've written.
*What to look for:* Practical experience with middleware for authentication, logging, error handling, and request processing.
Advanced Questions
Performance and Scaling
Q: How would you optimize a Node.js application that's becoming slow?
*What to look for:* Profiling tools knowledge, understanding of common bottlenecks (blocking operations, memory leaks), caching strategies, and clustering.
Q: Explain the cluster module and when you would use it.
*What to look for:* Understanding of multi-core utilization, load balancing, and process management for production applications.
Security
Q: What security considerations are specific to Node.js applications?
*What to look for:* Knowledge of input validation, SQL/NoSQL injection prevention, dependency vulnerabilities, OWASP guidelines, and secure session management.
Practical Assessment
Beyond questions, evaluate through:
Red Flags to Watch For
Expert Hiring Assistance
At FYB Technologies, our technical team pre-screens all developers using rigorous assessments, including these types of questions. We ensure you only interview candidates who meet your technical requirements.
Let us handle the initial screening while you focus on finding the perfect culture fit.