Is the architecture of Node.js single-threaded or does it use multithreading within the operating system?

The architecture of Node.js is based on a single-threaded event loop that handles asynchronous operations in a single JavaScript thread.

However, under the hood, Node.js uses the operating system's multithreading capabilities to perform heavy operations such as file I/O, network requests, and cryptography through the libuv thread pool.

Thus, from the perspective of JavaScript code — it is a single-threaded process, but in the implementation of Node.js, system threads are used for efficient handling of asynchronous tasks.