Node.js is a single-threaded application. How does it handle multiple concurrent requests?

Node.js operates on a single-threaded Event Loop, which allows efficient handling of many concurrent requests without creating new threads for each.

Main mechanisms:

• Asynchronous input/output (I/O) operations do not block the Event Loop. For example, reading files, database queries, and network operations are performed in the background.
• When an operation completes, a callback or promise is invoked, and the Event Loop continues processing.

Thus, Node.js does not create a new thread for each request but uses a non-blocking asynchronous approach, enabling it to serve thousands of concurrent connections with minimal overhead.

Example:

const http = require('http');

const server = http.createServer((req, res) => {
  // Asynchronous operation, e.g., reading from a database
  someAsyncOperation().then(data => {
    res.end(data);
  });
});

server.listen(3000);

Here, the server does not block during the operation and continues to accept new requests.