Realtime Vote / Response Aggregation

Type: data Origin repo(s): baby-namer (canonical, tournament votes), reincarnation (item responses), vela (player signals) Extraction readiness: copy-paste bundle Depends on: Supabase (for Postgres changes broadcast) Last reviewed: 2026-04-24

What it is

User interactions (vote, pass, rate, respond) are written to a dedicated append-only table → Supabase Realtime broadcasts the INSERT over a channel named by the scoping entity → client channels subscribed to that scope receive the delta and update aggregated counts/rankings on screen with no page reload. Pattern solves the "live tallies without polling" problem without standing up a WebSocket server.

Data shape

• Append-only event table: { id, scope_id, event_type, payload JSONB, user_id?, created_at }.
• Aggregate view or materialized view keyed on scope_id that computes counts/ranks.
• Supabase Realtime subscription on the event table, filtered by scope_id = <channel key>.
• Optional: rate limit on writes per user to prevent spam.

UI / surface shape

• Client hook (e.g. useRealtimeAggregate(scopeId)) that subscribes on mount, handles INSERT events, merges into local state.
• UI elements that reflect live counts — vote bars, ranking lists, live participant counts.
• Graceful fallback: polling every N seconds if the realtime channel errors.

Variants in the wild

• Baby-namer — tournament matchup vote bars. Scope = matchup_id.
• Reincarnation — item response aggregation. Scope = survey_instance_id.
• Vela — player signal processing (aesthetic feedback events). Scope = player_id.

Primary files in origin

• db/supabase/realtime.ts (baby-namer) — channel helpers
• hooks/useRealtimeAggregate.ts — client subscription hook
• server/events/vote-writer.ts — write endpoint with rate limiting

Next-version notes

• The "channel-name-by-scope" pattern (P57) is clean and already domain-agnostic; could be packaged as a shared hook in the consolidated monorepo.
• Fallback polling is currently per-app; should become a shared concern.
• When channel count grows, consider server-derived aggregates rather than client-computed to avoid re-running reducer logic in every tab.

Related patterns

• P57 — Realtime fan-out by channel naming
• P32 — Append-Only Signal Capture
• P41 — Polling Status Endpoint (as fallback when realtime errors)