# PostgreSQL backup demand and cost model — 2026-08-10

## Observed baseline

A read-only query against `platform-pg-1` at `2026-08-10T15:54:12Z` measured
39,573,871 bytes across connectable databases. `pg_stat_wal` reported
19,744,568 bytes since `2026-08-10T13:37:53Z`, an extrapolated 0.208 GB/day.
The cluster is less than one day old, so this is a seed observation rather than
a representative trend. No credential value was read or recorded.

The governed requirements are a 30-day recovery window, daily physical base
backup, continuous WAL archive, one monthly restore drill, and a complete exit
calculation. The scenario inputs live in
`data/demand/platform-audit-storage.json` and deliberately floor demand above
the tiny initial observation:

| Scenario | Initial DB | Monthly growth | WAL/day | Restore egress | Labor/month |
| --- | ---: | ---: | ---: | ---: | ---: |
| low | 1 GB | 5% | 0.25 GB | 1 GB | 0.5 h |
| base | 5 GB | 10% | 1 GB | 5 GB | 1 h |
| high | 20 GB | 20% | 5 GB | 20 GB | 2 h |

The conservative stored-byte formula is `30 × current database size + 30 ×
daily WAL`. It does not claim compression savings. Operator labor is valued at
€60/hour; provider-specific labor floors capture relative operational effort.
The exit event adds full stored-byte egress plus four operator hours.

Run `make forecast` for all 12 months, scenarios, and providers. A `null` total
is intentional: it means a required price is unknown and prevents an unknown
from silently becoming free.

The catalog also includes self-managed Garage on 1–3 Host Europe/Hetzner VMs
and managed AWS, Azure, Google Cloud, and STACKIT price points. See
`RESOURCE-WP-0002-expanded-storage-comparison-2026-08-10.md` for assumptions
and topology warnings.

Calculator rows split `monthly_infrastructure_eur` from
`monthly_internal_labor_eur` and split internal setup labor from external setup
services. The top-level `comparison_320gb` array provides a normalized running
cost at 320 GB using the base request and restore pattern.

## Initial comparison

- Scaleway Standard Multi-AZ is fully calculable at €0.01606/GB-month, with
  75 GB/month free egress then €0.01/GB. Prices exclude tax.
- Hetzner is calculable while usage remains inside its €6.49 monthly minimum,
  which includes 1 TB storage and 1 TB egress. Excess unit prices still need to
  be captured before high-growth or exit usage crosses the included quota.
- Host Europe cannot be calculated until it confirms that the historical S3
  Cloud Storage product is currently orderable and supplies a current quote.

Because labor dominates this very small workload, selection should emphasize
restore compatibility, independent failure domain, encryption, and exit proof
before sub-euro storage differences.