Custom Analytics: "This site, measured"

A public, in-site analytics product built end-to-end, the flagship engineering proof. Decision + trade-offs: D008 - Fully Custom Analytics.

Pipeline (all yours): custom ~3KB tracker → /api/track ingest → Neon Postgres + Upstash Redis → /api/insights (cached) → custom dashboard

• Tracker: cookieless, lazy after LCP, one delegated click listener → {section, element, x%, y%}; scroll depth + time-on-section; named events (demo_used, cta_click, lang_change, theme_change); sendBeacon batching; DNT-aware.
• Ingest: validate, rate-limit, bot-filter, derive country from IP then discard IP.
• Dashboard (/analytics + teaser): live visitors, top sections, click map, scroll-depth curve, device/referrer/locale splits, landed→work→demo→contact funnel. Accessible chart alternatives.

Ties to Internationalization (locale split) and is the "I measure" beat of North Star - Site as Proof. Privacy note on the page is itself a maturity signal. Scaling answer: columnar store (ClickHouse/Tinybird) at real scale.

As built (Phase 4 - Analytics): 2.1KB tracker; env-driven POSTGRES_URL + REDIS_URL; country via x-vercel-ip-country (IP never parsed); session id in tab-scoped sessionStorage (cookieless, anonymous) for MPA funnel continuity; DNT + GPC make it inert. Prod storage wired at launch (D017 - Defer External Service Activation).