Node.js has been at the center of web development for years, yet it is still surrounded by myths. The biggest source of confusion is how it handles concurrency. Let's separate the myths from the realities.
Myth: "Single-threaded means slow"
Node runs your JavaScript on a single main thread, which leads people to assume it can't handle load. In practice, Node excels at I/O-heavy workloads precisely because it doesn't block that thread waiting on the network or disk.
Reality: asynchronous, not parallel
Asynchronous and parallel are not the same thing. Asynchronous means Node starts an operation and continues working instead of waiting. Parallel means multiple things execute at the literal same instant. Node's event loop gives you enormous concurrency without true parallelism for your JS code.
The event loop
The event loop is the heart of Node. It offloads I/O to the system, registers callbacks, and processes them as results arrive — keeping the main thread free to handle thousands of connections efficiently.
When you do need parallelism
CPU-bound work — image processing, heavy computation — can block the event loop. For that, Node offers worker threads and clustering to spread load across cores. The trick is knowing which kind of work you have.
The takeaway
Node is a superb fit for I/O-bound, high-concurrency services. Understand the event loop, reach for worker threads when work is CPU-bound, and most "Node is slow" myths disappear.