How do you monitor APIs in production?

const morgan = require('morgan');
const winston = require('winston');

// Request logging
app.use(morgan(':method :url :status :response-time ms'));

// Structured logging
const logger = winston.createLogger({
  format: winston.format.json(),
  transports: [
    new winston.transports.File({ filename: 'error.log', level: 'error' }),
    new winston.transports.File({ filename: 'combined.log' }),
  ],
});

// Log API calls
app.use((req, res, next) => {
  const start = Date.now();
  res.on('finish', () => {
    logger.info({
      method: req.method,
      url: req.url,
      status: res.statusCode,
      duration: Date.now() - start,
      userAgent: req.get('user-agent'),
    });
  });
  next();
});

app.get('/health', async (req, res) => {
  const health = {
    status: 'ok',
    timestamp: new Date().toISOString(),
    uptime: process.uptime(),
    checks: {
      database: await checkDatabase(),
      redis: await checkRedis(),
    },
  };

  const isHealthy = Object.values(health.checks).every(c => c.status === 'ok');
  res.status(isHealthy ? 200 : 503).json(health);
});