Node.js is primarily single-threaded for its JavaScript execution as a deliberate architectural choice to maximize efficiency and simplicity for I/O-intensive web applications. The event loop, aka the main thread, allows running one thing at a time.
By using a single thread (the Event Loop) to manage application logic, Node.js avoids the significant resource overhead and complexity associated with traditional multi-threaded servers.
With a single thread, developers don't need to manage thread creation, synchronization, or race conditions, which makes the programming model simpler and less error-prone.
Single threaded event loop eliminates the overhead associated with managing multiple threads, such as context switching and memory usage.
A single-threaded architecture consumes fewer system resources compared to multi-threaded systems, especially for handling a large number of lightweight tasks.
JavaScript, the language underlying Node.js, was originally designed for single-threaded environments (like browsers). Node.js embraced this model to stay aligned with JavaScript's characteristics.
The problem with multithreading is it requires communication between threads to share tasks to avoid repeating already completed tasks.
Multithreading is not always easy because in the end we have only one physical processor that takes care of the execution and it’s just mimicking the tasks getting done parallelly but in reality, it just jumps between tasks back and forth.
There is also a very well-known and criticized issue with the one thread per request model for a server which is that they don’t scale very well for several scenarios compared to the event loop thread model, in short, they lack scalability as the application grows to meet the future demands and with the addition of new features.
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