Node.js & Express

instrument.js — first import wins

// instrument.js — MUST be imported before anything else
import * as Sentry from '@sentry/node';

Sentry.init({
  dsn: 'https://<publicKey>@jentry.app/<projectId>',
  environment: process.env.NODE_ENV,
  tracesSampleRate: 0.1,
});

// index.js
import './instrument.js'; // ← first
import * as Sentry from '@sentry/node';
import express from 'express';

const app = express();
// …routes…

Sentry.setupExpressErrorHandler(app); // before your own error middleware
app.use(myErrorHandler);
app.listen(3000);

What you get

• Unhandled exceptions and rejections as grouped issues with release/environment tags.
• Each request as a transaction with db/http child spans — the waterfall shows exactly where time went.
• Automatic N+1-query and slow-query issues detected from those spans, with span evidence.
• Cron check-ins via Sentry.withMonitor / the check-in API — see the Crons guide.