Node.js Architecture

Key Characteristics:

Non - blocking I/O, event - driven, single - threaded with event loop, asynchronous execution

Each request is added to the

Event Queue

The Event Loop continuously checks the

Event Queue

Simple (non - blocking) tasks are handled immediately by the main thread
Complex/blocking tasks are offloaded to the Thread Pool

Callback Queue

Event Loop processes callbacks and sends responses

Non-blocking Examples

console.log('Before file read');
fs.readFile('myfile.txt', 'utf8', (err, data) => {
if (err) throw err;
console.log('File contents:', data);
});
console.log('After file read');
Notice how "After file read" is printed before the file contents, showing that Node.js does not wait for the file operation to finish.

Example: Blocking vs Non-blocking Code

// Blocking code example console.log('Start of blocking code');
const data = fs.readFileSync('myfile.txt', 'utf8'); // Blocks here console.log('Blocking operation completed');
// Non-blocking code example console.log('Start of non-blocking code');
fs.readFile('myfile.txt', 'utf8', (err, data) => {
if (err) throw err;
console.log('Non-blocking operation completed');
});
console.log('This runs before the file is read');

Key Difference:

Node.js is particularly well - suited for:

I/O-bound applications

Real-time applications

APIs

Microservices

Note:

Node.js may not be the best choice for CPU - intensive tasks as they can block the event loop. For such cases, consider:

Using worker threads

Using native add-ons

Summary

Node.js is fast and efficient because it uses a non - blocking event loop and delegates heavy work to the system.

Key Benefits:

Handles many concurrent connections efficiently

Great for I/O-bound applications

Uses JavaScript on both client and server