---

name: sentry-performance-monitoring description: Use when setting up performance monitoring, distributed tracing, or profiling with Sentry. Covers transactions, spans, and performance insights. allowed-tools:

• Read
• Write
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• Grep
• Glob

---

Sentry - Performance Monitoring

Track application performance with transactions, spans, and distributed tracing.

Enable Performance Monitoring

Copyimport * as Sentry from "@sentry/browser";

Sentry.init({
  dsn: "...",
  tracesSampleRate: 0.2, // 20% of transactions
  integrations: [
    Sentry.browserTracingIntegration(),
  ],
});

Transactions

Automatic Transactions

Copy// Browser: Page loads and navigations
Sentry.init({
  integrations: [
    Sentry.browserTracingIntegration({
      tracePropagationTargets: ["localhost", /^https:\/\/api\.example\.com/],
    }),
  ],
});

Manual Transactions

Copyconst transaction = Sentry.startTransaction({
  op: "task",
  name: "Process Order",
});

try {
  // Your code here
  processOrder(order);
  transaction.setStatus("ok");
} catch (error) {
  transaction.setStatus("internal_error");
  throw error;
} finally {
  transaction.finish();
}

Spans

Create Child Spans

Copyconst transaction = Sentry.startTransaction({ name: "checkout" });

const validationSpan = transaction.startChild({
  op: "validation",
  description: "Validate cart items",
});
await validateCart(cart);
validationSpan.finish();

const paymentSpan = transaction.startChild({
  op: "payment",
  description: "Process payment",
});
await processPayment(payment);
paymentSpan.finish();

transaction.finish();

Span Data

Copyconst span = transaction.startChild({
  op: "db.query",
  description: "SELECT * FROM users WHERE id = ?",
  data: {
    "db.system": "postgresql",
    "db.name": "production",
  },
});

Distributed Tracing

Propagate Trace Context

Copy// Frontend
Sentry.init({
  integrations: [
    Sentry.browserTracingIntegration({
      tracePropagationTargets: [
        "localhost",
        /^https:\/\/api\.yoursite\.com/,
      ],
    }),
  ],
});

// This automatically adds sentry-trace and baggage headers

Backend Continuation

Copy// Express.js
import * as Sentry from "@sentry/node";

app.use(Sentry.Handlers.requestHandler());
app.use(Sentry.Handlers.tracingHandler());

// The transaction is automatically continued from incoming headers

Sampling

Static Sampling

CopySentry.init({
  tracesSampleRate: 0.1, // 10% of transactions
});

Dynamic Sampling

CopySentry.init({
  tracesSampler: (samplingContext) => {
    // Always sample errors
    if (samplingContext.parentSampled !== undefined) {
      return samplingContext.parentSampled;
    }

    // High priority endpoints
    if (samplingContext.name.includes("/checkout")) {
      return 1.0;
    }

    // Don't sample health checks
    if (samplingContext.name.includes("/health")) {
      return 0;
    }

    // Default rate
    return 0.1;
  },
});

Web Vitals

Copy// Automatically captured with browserTracingIntegration
// LCP, FID, CLS, FCP, TTFB

Sentry.init({
  integrations: [
    Sentry.browserTracingIntegration({
      enableLongTask: true, // Track long tasks
    }),
  ],
});

Custom Metrics

Copy// Capture custom metrics
Sentry.metrics.increment("button_clicked", 1, {
  tags: { button: "checkout" },
});

Sentry.metrics.distribution("cart_value", cart.total, {
  unit: "dollar",
  tags: { currency: "USD" },
});

Sentry.metrics.gauge("active_users", activeCount);

Sentry.metrics.set("unique_visitors", visitorId);

Profiling

Copy// Node.js
import * as Sentry from "@sentry/node";
import { nodeProfilingIntegration } from "@sentry/profiling-node";

Sentry.init({
  dsn: "...",
  integrations: [nodeProfilingIntegration()],
  tracesSampleRate: 1.0,
  profilesSampleRate: 1.0,
});

Best Practices

1. Start with low sample rates, increase as needed
2. Use dynamic sampling for important transactions
3. Propagate trace context to all services
4. Add meaningful span descriptions
5. Track business-critical user flows
6. Use custom metrics for business KPIs
7. Enable profiling for performance-critical code