When would you use cluster module in Node.js?

The Node.js cluster module is used to enhance the performance and scalability of an application by allowing it to run multiple worker processes across multiple CPU cores. You would use the cluster module in Node.js in the following scenarios:

1. To Utilize Multi-Core Systems: Modern servers often have multiple cores. Node.js runs in a single thread by default, which means it does not take full advantage of multi-core systems. The cluster module allows you to create child processes that run simultaneously, each on its own thread, to handle the load[1][3][8][9][11][13].

2. For CPU-Intensive Applications: If your Node.js application performs CPU-intensive tasks, such as data processing or complex calculations, clustering can help distribute these tasks across multiple cores, preventing any single thread from becoming a bottleneck[1][2][3][10].

3. To Improve Application Throughput: By distributing incoming connections and requests across multiple workers, clustering can increase the number of requests your application can handle at any given time, improving throughput and reducing response times[3][7][9][10].

4. To Enhance Reliability and Fault Tolerance: The cluster module can improve the reliability of an application. If a worker process crashes, the master process can spawn a new worker, ensuring that the application continues to handle requests without significant downtime[1][3][12].

5. For Load Balancing: The cluster module can act as a load balancer, distributing incoming network connections evenly across the worker processes. This helps in managing the load more efficiently and prevents any single worker from being overwhelmed[3][7][11].

6. To Reduce Latency: For applications that require low latency, clustering can help by ensuring that there is always a worker available to handle a request, thus reducing the time it takes for a request to be processed[3][10].

7. When Scaling Applications Horizontally: If you need to scale your application horizontally on a single machine, clustering is a straigh...