Your first challenge

import express from 'express';
import { Metrics, MetricUnit } from '@aws-lambda-powertools/metrics';

// Glass Garden gives every instance its own PORT, because they all share one machine here.
// In a real deployment they would each be on their own machine, and could all listen on the same port.
const port = Number(process.env.PORT);
if (!port) {
  throw new Error('PORT is not set');
}

// CloudWatch metrics, written the way a Lambda writes them: as a line on stdout that the
// Metrics tab reads. Each addMetric is one observation, not a running total
const metrics = new Metrics();
// What tells one instance's numbers from another's, here and in CloudWatch: a dimension the
// code declares. Remove it and the instances' lines merge into one
metrics.setDefaultDimensions({ instance: String(port) });

const app = express();

app.get('/', (req, res) => {
  metrics.addMetric('requests', MetricUnit.Count, 1);
  metrics.publishStoredMetrics();

  // One name on the line below is not the one this file declares, so every request ends in a
  // 500 instead of an answer. The Logs tab has the error and the line it came from, and the
  // generator's Metrics tab has the failures it is counting
  res.type('text/plain').send(`Hello from the instance on :${instancePort}\n`);
});

// Express hands a failed request here, which is what puts one readable line in the Logs tab
// instead of a raw stack trace. Browsers do not agree on what a stack even contains
app.use((error, req, res, next) => {
  console.error(`${error.name}: ${error.message}`);
  res.status(500).type('text/plain').send('Something went wrong\n');
});

app.listen(port, () => {
  console.log(`Server running on http://localhost:${port}`);
});