Real-Time Node.js Processing App

I need a production-ready Node.js application capable of handling real-time data streams with very low latency. The service will ingest continuous input, run custom business logic on the fly, and push the processed results out immediately—think WebSocket or Socket.io feeds, but I am open to the framework you feel is most suitable.

Clean, modular code, solid error handling, and unit tests are essential. Please structure the project so it can scale horizontally (stateless design, queue or pub/sub friendly). A brief README that explains local setup, environment variables, and start-up commands will be required.

When you respond, focus on your previous experience building real-time Node.js systems—mention any relevant projects, peak throughput numbers, or performance optimizations you implemented.

Deliverables:
• Complete source code in a Git repository
• Package.json with all dependencies and scripts
• README covering setup, build, and run instructions
• Basic test suite demonstrating core processing logic

If you have questions about the data format or deployment environment, let me know and we can clarify before you start coding.