{"slug": "one-npx-command-to-see-why-your-website-is-slow-new-relic-sentry-on-localhost", "title": "One npx command to see why your website is slow (New Relic + Sentry on localhost)", "summary": "A developer has released MetricFlow, an open-source local dashboard that runs via a single npx command and displays New Relic real-user performance metrics alongside Sentry JavaScript errors per page. The tool requires users to supply their own New Relic and Sentry API keys, keeps all data on the local machine, and optionally uses Gemini, Claude or OpenAI to generate prioritized fix suggestions. It is described as early, work-in-progress software requiring Node >=20.12.", "body_md": "I'm building **MetricFlow**, a performance dashboard for your website that runs on your own machine. It shows real-user metrics from **New Relic** and JavaScript errors from **Sentry** side by side, per page, and can suggest what to fix first.\n\nThat opens a dashboard at `http://localhost:3000`. There is no MetricFlow server and no account to create. Your keys stay on your machine.\n\n**Status:** early, work in progress. Things will change, and feedback is very welcome.\n\n*Sample data, not real numbers.*\n\n## \n  \n  \n  What you get\n\n- \n**Dashboard:** average response time, error rate, throughput and Apdex, plus TTFB, LCP and CLS cards with trends and a \"what moved since the last check\" list.\n- \n**Performance hub:** every tracked page with its health (Healthy, Warning or Critical) and a detail view per page.\n- \n**Tool pages:** New Relic numbers only, or Sentry errors only, per page.\n- \n**AI suggestions (optional):** Gemini, Claude or OpenAI turns your numbers into a short \"fix this first\" list. Bring your own key.\n\n## \n  \n  \n  Try it in four steps\n\n1. \n**Start it:**`npx @karan171996/metricflow` . The first run shows \"Connect your data\".\n2. \n**Add your keys:** a New Relic User API key and account ID, and a Sentry auth token, organization slug and project slug. Paste them on the Setup page or put them in a`.env.local` file.\n3. \n**Send data from your site:** MetricFlow only reads. The`/connect` page gives you copy-paste snippets for the New Relic Browser agent and Sentry.\n4. \n**Check that data arrives:** the same page shows a row per source that turns green when events come in. Then open the dashboard.\n\nYou need Node `>=20.12`. New Relic and Sentry both have free plans, which is enough to try it.\n\n## \n  \n  \n  Good to know\n\n- It is early software. Expect rough edges.\n- It is a local tool, not a hosted service. It runs on your machine while you use it.\n- Everything runs with your own keys, and nothing is sent anywhere except to New Relic, Sentry and, if you turn it on, your chosen AI provider.\n\n## \n  \n  \n  Try it and tell me what you think\n\nIf you run it against your own site, I'd like to hear what was confusing in setup and which numbers you expected to see and didn't. Leave a comment below.", "url": "https://wpnews.pro/news/one-npx-command-to-see-why-your-website-is-slow-new-relic-sentry-on-localhost", "canonical_source": "https://dev.to/karan171996/one-npx-command-to-see-why-your-website-is-slow-new-relic-sentry-on-localhost-31g1", "published_at": "2026-10-03 05:00:16+00:00", "updated_at": "2026-10-03 05:07:45.395044+00:00", "lang": "en", "topics": ["developer-tools", "ai-tools"], "entities": ["MetricFlow", "New Relic", "Sentry", "Gemini", "Claude", "OpenAI", "Node.js"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/one-npx-command-to-see-why-your-website-is-slow-new-relic-sentry-on-localhost", "markdown": "https://wpnews.pro/news/one-npx-command-to-see-why-your-website-is-slow-new-relic-sentry-on-localhost.md", "text": "https://wpnews.pro/news/one-npx-command-to-see-why-your-website-is-slow-new-relic-sentry-on-localhost.txt", "jsonld": "https://wpnews.pro/news/one-npx-command-to-see-why-your-website-is-slow-new-relic-sentry-on-localhost.jsonld"}}