rum-core

A lightweight Real User Monitoring (RUM) tool. A ~5kb browser script intercepts fetch() and XHR calls, captures timing and environment data, and sends it to an edge worker for enrichment and storage. Developers get visibility into what real users experience — broken down by ISP, region, device, and more.

What It Tracks

• Core Web Vitals — LCP, FCP, CLS, INP (via web-vitals/slim)
• API Performance — DNS, TCP, TLS, TTFB, duration for every fetch/XHR call
• User Environment — browser, OS, device type, screen resolution, connection type
• Geo & Network — country, city, region, ISP (enriched at the edge via Cloudflare Workers)

How It Works

Browser Script (~5kb)
  ├─ Web Vitals → fires once per page load
  └─ Request Events → batched every 10s
       ↓
Cloudflare Worker (enrich with geo/ISP, hash IP)
       ↓
Turso (event storage)
       ↓
Dashboard (Next.js + Bun/Elysia backend)

Monorepo Structure

rum-core/
├── apps/
│   ├── web/          → Next.js frontend (dashboard)
│   ├── api/          → Bun + Elysia backend
│   └── worker/       → Cloudflare Worker (ingest)
├── packages/
│   ├── db/           → Drizzle schemas + clients (Neon + Turso)
│   ├── shared/       → Shared types, constants, utilities
│   └── script/       → Browser script (rum-core.js)

Tech Stack

Layer	Stack
Browser Script	Vanilla JS (~5kb), esbuild, web-vitals/slim
Edge Worker	Cloudflare Workers, Hono
Backend	Bun, Elysia, Drizzle ORM
Frontend	Next.js (SSG), SWR, Tailwind CSS, shadcn/ui
Event DB	Turso (SQLite)
Business DB	Neon (Postgres)

Getting Started

bun install

# run the frontend
bun run dev --filter=web

# run the backend
bun run dev --filter=api

Documentation

For detailed architecture, database schemas, rollup table design, cron jobs, dashboard routing, and subscription plans — see planning.md.