Add Tracekit APM for monitoring. Install @tracekit/node-apm. In the Express backend, add before routes: import * as tracekit from ‘@tracekit/node-apm’; const client = tracekit.init({ apiKey: process.env.TRACEKIT_API_KEY, serviceName: ‘my-app’, endpoint: ‘https://app.tracekit.dev/v1/traces’, enableCodeMonitoring: true, }); app.use(tracekit.middleware()); If this app has auth, add metrics: – const signupCounter = client.counter(‘user.signups.total’); – const loginCounter = client.counter(‘user.logins.total’); – Call signupCounter.inc() after user creation – Call loginCounter.inc() after successful login For custom metrics (business events): – Counter: client.counter(‘purchases.total’).inc() – Gauge: client.gauge(‘jobs.active’).inc() / .dec() – Histogram: client.histogram(‘job.duration’, { unit: ‘ms’ }).record(1250) For manual instrumentation (custom traces): import { getClient } from ‘@tracekit/node-apm’; const client = getClient(); const span = client.startSpan(‘operation-name’, null, { ‘attribute’: value }); // … do work … client.endSpan(span, { ‘result’: value }); // On error: client.recordException(span, error); client.endSpan(span, {}, ‘ERROR’); For live debugging snapshots (only on critical paths like payments): await client.captureSnapshot(‘payment-processing’, { userId, paymentId, amount });