Build HTTP APIs with routing, middleware, validation, controllers, and error handling.
Lessons
Reuse database connections for performance and stability.
Connection Pooling is easiest to learn by reading the example, changing it, and observing the result.
import express from 'express';
const app = express();
app.use(express.json());
app.get('/api/lessons', (req, res) => {
res.json([{ slug: 'express-routing', title: 'Express Routing' }]);
});
app.post('/api/lessons', (req, res) => {
res.status(201).json({ created: true, title: req.body.title });
});
app.listen(process.env.PORT || 3000);Practice the Connection Pooling example in a small scratch file, then explain what changed and why.