# Excititor · Graph Indexes Prep (GRAPH-21-005)

- **Date:** 2025-11-20
- **Depends on:** GRAPH-21-002 overlays
- **Working directory:** `src/Excititor/__Libraries/StellaOps.Excititor.Storage.Mongo`

## Index plan
- Collection: `vex_observations`
  - Compound index `{ tenant: 1, component.purl: 1, advisoryId: 1, source: 1, modifiedAt: -1 }` (supports overlay queries and truncation cursor).
  - Sparse index `{ tenant: 1, component.purl: 1, status: 1 }` for summary counts.
- Collection: `vex_overlays` (materialized cache, optional)
  - Index `{ tenant: 1, purl: 1 }` unique.
  - TTL index on `cachedAt` configurable via `excititor:graph:overlayTtlSeconds`.

## Determinism
- Materialization job must sort observations as per GRAPH-21-001 ordering before writing overlays so pagination/cursors align.
- TTL applied identically across tenants; default 300s, override allowed via config but must be documented.

## Acceptance for prep completion
- Index keys and TTL knobs defined; downstream storage tasks can implement without further contract churn.