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Appendix: service limits

Applies to SWATGenX engine extensions · Updated August 2026

Size, storage, concurrency, and coverage limits enforced on model generation — engineering constants from the live order paths and storage policy.

Limits below are taken from the live Flask order paths and storage policy. Prefer this page over older public API markdown that still documents Basic ≤15 HUC12 and HUC8-as-Pro-only.

Storage-first tiers

  • Basic default storage: 2 GB (SWATGENX_BASIC_STORAGE_LIMIT_BYTES).
  • Pro / extended default storage: 20 GB (SWATGENX_PRO_STORAGE_LIMIT_BYTES).
  • Basic retention: 30 days after creation (SWATGENX_BASIC_RETENTION_DAYS); Pro has no scheduled cleanup.
  • Concurrency: Basic 1 build at a time; Pro up to 3 (extras queue). Env: SWATGENX_BASIC_MAX_CONCURRENT_BUILDS / SWATGENX_PRO_MAX_CONCURRENT_BUILDS.
  • Over storage quota → new orders blocked for any basin size (reason storage_limit).

Explorer outlet-HUC12 size cap (Basic)

  • POST /api/model-settings/explorer-watershed: Basic accounts reject resolved watersheds larger than SWATGENX_BASIC_MODEL_MAX_HUC12 (default 35) with error_code model_basic_huc12_cap.
  • The same gate message notes the HUC8 order path as the way to take one full HUC8 on Basic.
  • All tiers: watershed must lie in a single VPUID (error_code model_cross_vpuid); cross-VPU basins can be explored but not ordered yet.
  • Pro explorer safety ceiling for very large single-region walks defaults to 300 HUC12 (SWATGENX_EXPLORER_MAX_WATERSHED_PRO), clamped 16–500.

Station, HUC8, HUC14 paths

  • POST /api/model-settings (USGS station): storage + fair-use quotas apply; the old Basic ≤15 contributing-HUC12 hard block is not applied on this path (huc12_count is still recorded).
  • POST /api/model-settings-huc8: open to every tier — storage quota is the limit, not a Pro-only flag.
  • HUC14 / catchment orders: available on every tier; storage_gate is the constraint (not a separate Pro feature gate).

Fair-use and Pro-only features

  • Basic: up to 5 SWAT+ model orders per UTC calendar day (BASIC_DAILY_MODEL_LIMIT) and a lifetime allocation of 3 completed models on the free tier (BASIC_LIFETIME_MODEL_ALLOCATION); failed builds are refunded.
  • Calibration / validation flags on model creation are Pro-only (code calval_pro_only).
  • SWAT+MODFLOW-6: Pro + groundwater coverage (MI Lower Peninsula, IN, WI, OH) via validate_modflow_addon — see the MODFLOW coupling chapter. Advanced QSWAT/resolution knobs also follow Pro / extended-access checks in the order handlers.
Flood / PDF report paths may still reference BASIC_MAX_HUC12_SUBBASINS = 15 for report eligibility — that constant is separate from the explorer model-order cap of 35.