31. What is event-driven architecture?

Event-driven architecture is a system design style where communication between components occurs through events. Components emit events that are received and handled by other components. This is an asynchronous approach that enables loose coupling between system components.

Advantages of event-driven architecture:

1. Scalability: Easily scalable, as components can operate independently and respond to events in real time.
2. Flexibility: Components can be easily added, removed, or modified without affecting other parts of the system.
3. Reactivity: Event-driven systems can respond immediately to changes in application state, which is crucial for real-time applications.
4. Loose coupling: Components are loosely coupled, making independent development and deployment easier.

Example of using event-driven architecture in Node.js:

const EventEmitter = require('events');
class MyEmitter extends EventEmitter {}

const myEmitter = new MyEmitter();

// Event handling
myEmitter.on('event', () => {
  console.log('An event occurred.');
});

// Emitting an event
myEmitter.emit('event');

Event-driven architecture is ideal for applications requiring high scalability and flexibility, such as IoT systems, financial applications, and real-time applications.