Question 1

How do you implement a WebSocket server in Node.js?

Accepted Answer

WebSockets enable real-time, two-way communication. Use the 'ws' library in Node.js.
- Create a server that upgrades HTTP to WebSocket.
- Handle messages, connections, and disconnections.
- Ideal for chat apps or live updates.
- Scales with clustering.

Question 2

How would you design a RESTful API in Node.js?

Accepted Answer

Designing a RESTful API in Node.js involves defining routes, HTTP methods, and responses following REST principles.
- Use Express for routing and middleware.
- Structure endpoints (e.g., /users/:id) logically.
- Return consistent status codes and JSON data.
- Implement versioning for scalability.

Question 3

How do you optimize static asset delivery in Node.js?

Accepted Answer

Optimizing static assets improves app performance.
- Use compression (e.g., gzip) with 'compression' middleware.
- Set caching headers (ETag, Cache-Control).
- Serve via a CDN for global reach.
- Minify CSS/JS with tools like UglifyJS.

Question 4

How do you implement a pub/sub system in Node.js?

Accepted Answer

Pub/sub enables event-driven communication.
- Use Redis or a custom EventEmitter for simple setups.
- Publishers emit events; subscribers listen.
- Scales with message queues (e.g., RabbitMQ).
- Great for real-time apps.

Question 5

What is the 'worker_threads' module in Node.js?

Accepted Answer

The 'worker_threads' module enables multi-threading in Node.js for CPU-bound tasks.
- Each worker runs in its own thread with isolated memory.
- Communicates via message passing.
- Introduced in Node v10, stable in v12.
- Complements the Event Loop for I/O.

Question 6

How can you improve the performance of a Node.js application?

Accepted Answer

Optimizing a Node.js app involves several strategies.
- Use clustering to leverage multiple CPU cores.
- Cache frequently accessed data with tools like Redis.
- Minimize synchronous code to avoid blocking.
- Profile with tools like Node.js’s --inspect to find bottlenecks.

Question 7

How do you implement caching in a Node.js application?

Accepted Answer

Caching improves performance by storing frequently accessed data.
- Use in-memory stores like Node’s Map or external ones like Redis.
- Cache API responses or database queries.
- Set expiration times to keep data fresh.
- Reduces server load and latency.

Question 8

How do you handle memory leaks in a Node.js application?

Accepted Answer

Memory leaks occur when unused objects aren’t freed. To handle them:
- Use tools like --inspect or heapdump to identify leaks.
- Avoid global variables and unclosed event listeners.
- Profile with Chrome DevTools or clinic.js.
- Ensure streams and promises are properly resolved.

Question 9

How do you design a microservices architecture with Node.js?

Accepted Answer

Microservices split an app into small, independent services.
- Use Node.js for lightweight, fast services.
- Communicate via REST, gRPC, or message queues (e.g., RabbitMQ).
- Deploy with Docker and orchestrate with Kubernetes.
- Ensure loose coupling and scalability.

Question 10

How do you monitor a Node.js application in production?

Accepted Answer

Monitoring ensures a Node.js app runs smoothly.
- Use PM2 for process health and logs.
- Integrate tools like New Relic or Prometheus for metrics.
- Track CPU, memory, and response times.
- Set up alerts for failures or thresholds.

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