High CPU usage in a Node.js application typically occurs when the application runs CPU-bound tasks, such as complex calculations, file parsing, or heavy data transformations. Since Node.js is single-threaded, these tasks can block the event loop and cause high CPU usage, leading to sluggish performance. To reduce CPU usage, one solution is to offload CPU-intensive tasks to Node.js Worker Threads, which allow you to run these operations in parallel threads without affecting the main event loop. Alternatively, you can optimize your algorithms or code structure to avoid inefficient loops or recursive operations that consume excessive CPU resources. Profiling tools like `clinic` or `0x` can help you identify bottlenecks in your code and find areas for optimization. In some cases, rewriting performance-critical sections of your code in a lower-level language like C++ using Node.js native addons can also significantly reduce CPU load. Efficient CPU management is key to maintaining high-performance Node.js applications, especially when scaling to handle high traffic.