The microservices model proposes building an application as a set of small, autonomous, and specialized services. Each microservice handles a specific functionality, is deployed independently, and communicates with others through well-defined APIs.

# Where Does This Idea Come From?

The need to scale complex systems, maintain independent teams, and improve development times pushed the emergence of this architecture. Large companies like Netflix, Amazon, or Spotify adopted it to divide their monolithic systems into distributed services.

# Key Characteristics

• Decomposition by functionality or domains.

• Each microservice has its own database (data independence).

• Communication via HTTP/REST, gRPC, events, or other mechanisms.

• Independently scalable, deployable, and versionable.

# Everyday Analogy

Imagine a shopping mall. There's a clothing store, a bookstore, an ice cream shop. Each business has its own team, its own checkout, its own inventory. If one store closes, the mall keeps working. That's how microservices are: independent but collaborating.

# Technical Example (Realistic Architecture)

Suppose we are developing an e-commerce system. We use microservices to divide it into independent components. Here's what that might look like:

• Catalog Service: Exposes available products, prices, descriptions.
• Cart Service: Manages products added by the user before purchasing.
• Order Service: Receives orders from the cart, processes payments, generates confirmations.
• User Service: Handles authentication, profiles, shipping addresses.

Visual example of an e-commerce application with microservices vs. a traditional monolith.

# Code per Service (Node.js)

const express = require('express');
const app = express();

app.get('/catalog', (req, res) => {
  res.json([ { id: 1, name: 'Sneakers', price: 10000 } ]);
});

app.listen(3001);

const express = require('express');
const app = express();
app.use(express.json());

app.post('/cart', (req, res) => {
  // Cart logic
  res.status(201).send('Added');
});

app.listen(3002);

const express = require('express');
const app = express();

app.post('/order', (req, res) => {
  // Orders and payments logic
  res.send('Processed');
});

app.listen(3003);

const express = require('express');
const app = express();

app.get('/users/:id', (req, res) => {
  res.json({ id: req.params.id, name: 'John' });
});

app.listen(3004);

# When Is It Convenient to Use Them?

When a system grows significantly in functionality, teams, and user volume. Also when you need to scale certain parts more than others or use different technologies in each module.