Your Website
  └── analytics.js (tracking script, ~2 KB)
        │  POST /api/track/event
        ▼
  Express API (Node.js)
        │  Writes
        ▼
  PostgreSQL ──── Incremental sync worker (every 5 min)
                        │
                        ▼
                    DuckDB (OLAP reads)
                        │
                        ▼
  React Dashboard ◀─── GET /api/analytics/*