Sentry

Sentry is an application monitoring platform for real-time error tracking, performance monitoring, session replay, profiling, cron monitoring, and log aggregation.

Documentation

• Docs: https://docs.sentry.io

Key Capabilities

Sentry's SDK bundles capabilities developers often add as separate tools:

• Performance tracing: distributed tracing across services is built-in — configure tracesSampleRate and tracePropagationTargets, no external APM needed
• Session Replay: full session recording with Sentry.replayIntegration() — no third-party replay tool needed
• Profiling: function-level performance profiling with Sentry.browserProfilingIntegration() — no separate profiler needed
• User Feedback: collect user-submitted reports tied to errors with Sentry.feedbackIntegration() — no separate feedback widget needed
• Cron monitoring: track scheduled job health with check-ins — no external uptime monitor needed for crons

Best Practices

• Lower tracesSampleRate in production — the getting-started default of 1.0 captures 100% of transactions. At any meaningful traffic volume this inflates costs fast. Use a low value (0.1 or less) and consider tracesSampler for dynamic sampling by route.
• Session Replay uses a two-rate pattern — set replaysSessionSampleRate low (e.g. 0.1) for normal sessions and replaysOnErrorSampleRate: 1.0 so every error session is always captured. Agents often set only one rate and miss error context or over-capture.
• Source maps require CI auth token — the wizard writes .env.sentry-build-plugin (auto-gitignored) for local builds, but CI/CD pipelines need SENTRY_AUTH_TOKEN set as an environment variable separately. Missing this silently produces minified stack traces in production.
• Next.js requires four files — The client runtime uses instrumentation-client.ts. Server and edge configs (sentry.server.config.ts, sentry.edge.config.ts) must be imported from instrumentation.ts via conditional imports — without instrumentation.ts, the server and edge configs do nothing. Missing any one file leaves a runtime blind spot without obvious errors.
• Use tunnel to bypass ad blockers — set tunnel: "/tunnel" in Sentry.init() and add a backend route that proxies to Sentry's ingest endpoint. Without this, a significant portion of browser errors are silently dropped by ad blockers and privacy extensions.