Fomo

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Build me a social-proof notification tool that replaces Fomo: real recent activity shown on my site, from my own data, with nothing invented.

STACK
- Node 20+ with Fastify, SQLite through better-sqlite3
- One embeddable script, vanilla, under 8KB gzipped, from my own domain
- Server-rendered admin
- Caddy in front

THE DATA MODEL
- sources: id, kind, config_json, is_active — a webhook, a database view, a CSV upload, or an API push
- events: id, source_id, kind, actor_name, actor_location, subject, subject_url, image_path, amount_cents, currency, occurred_at, received_at, is_public
- rules: id, name, event_kinds_json, page_pattern, min_age_minutes, max_age_hours, display_seconds, gap_seconds, position, max_per_session
- impressions: id, event_id, rule_id, session_hash, shown_at, clicked_at, dismissed_at
- Every event carries the time it actually happened. Nothing is generated, ever, and the schema has no column that would let it be

THE HARD RULE
- This tool shows things that happened. There is no fake mode, no sample generator that can be left on in production, and no 'someone in Berlin' when nobody was in Berlin.
- Write that in the README and enforce it in the code: an event with no source and no occurred_at cannot be stored.
- Anonymise instead of inventing: a first name and a city, taken from the real record, and configurable down to 'someone' — the ceiling is what is true, the floor is what is polite

GETTING THE DATA IN
- A webhook endpoint with a shared secret, taking one event or a batch
- A pull adapter for a database view, run every minute
- A CSV import for a backfill
- Idempotency by external id: a retry does not show the same purchase twice
- Events older than the rule's maximum age are stored but never shown, because 'somebody bought this' in a notification means recently

SHOWING IT
- One notification at a time, in a corner, for N seconds, with a gap of M seconds before the next
- A per-session cap, because the fifth notification is worse than the first
- A per-page rule set: the pricing page shows purchases, the blog shows nothing
- Never covering navigation or the bottom bar on a phone; never blocking a click
- Dismissible, and a dismissal is remembered for the session
- Keyboard reachable and announced politely to a screen reader, or not announced at all — never interrupting

WHAT A NOTIFICATION SAYS
- A line of text with slots: name, location, subject, and how long ago
- The relative time is computed in the browser from the real timestamp and never rounded upwards
- An optional image and a link to the subject
- The template is per rule, and the interface previews it with a real recent event, never with a placeholder

MEASURING WHETHER IT WORKS
- Impressions, clicks, dismissals, and click-through per rule
- A/B: two templates on the same rule, split by session hash, with the split stated
- The honest metric is conversion on the pages where it ran against where it did not — the admin page says that plainly rather than showing a vanity number

PRIVACY
- The name shown is whatever the source sends; the README says to send a first name only
- Location from a local database file at country or city level, never finer
- Visitors are identified by a session-scoped salted hash: no cookie, no cross-site anything
- A person in the source data can be excluded by key, permanently

THE INTERFACE
- One page per rule: what it shows, where, how often, and a live preview
- A feed of recent events with a switch to hide one
- Dark and light, one accent

OPERATIONS
- .env: DATABASE_PATH, BASE_URL, WEBHOOK_SECRET, HASH_SALT, GEOIP_DB_PATH, ALLOWED_ORIGINS
- Migrations on boot, each once
- The payload endpoint answers from memory with an ETag
- Nightly backup off the machine, restore script
- Health endpoint that reports the age of the newest event, because a silent source is the failure mode here

WHAT MATTERS MOST
Ingestion honesty and the frequency rules. Build the webhook, the idempotency and the one-at-a-time display first. Then put it on a real page for a day: if you cannot say where every notification came from, the tool is doing the one thing it must never do.

Give me the repository, the embeddable script, migrations, .env.example, a seed of real-shaped events, and a README with deploy steps behind Caddy.