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summary: The time-series database: what it keeps for how long, its schema, backups and readers
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# Time-series database

Keeps every reading for two years (about 40 MB a month).

- Subscribes to `mqtt-broker.md`; schema: one measurement per metric, tags `house` and `node`.
- Version and size are in `state.md`; backups: see the backup job note when it exists.

## Retention and copies (since 2026-03-08)
- Two years of raw data, then hourly means. Backed up by `backup-job.md`; read by `dashboard.md`.