Historical charts depend on periodic inserts into Supabase Postgres, not on the browser remembering prior values. A scheduled job or edge function polls feeds and writes normalized rows keyed by user and probe.
Insert model
- Timestamp + user_id + probe_key uniquely identify a sample.
- Store temp, humidity, units as typed columns for fast chart queries.
- Skip insert if upstream fetch failed to avoid flatlines at zero.
Auth boundary
Row-level security ties history to signed-in users: Supabase auth flow. Only the service role or trusted server route should insert on schedule.
Consumption
Dashboard reads via history browsing; export via CSV export. Live path: home page fetch.