Update

docs/VEHICLES-API.md

@@ -38,7 +38,8 @@ Notes:
 
 ### Caching (Redis)
 - Keys: `dropdown:years`, `dropdown:makes:{year}`, `dropdown:models:{year}:{make}`, `dropdown:trims:{year}:{model}`, `dropdown:engines:{year}:{model}:{trim}`
-- Default TTL: 6 hours
+- Default TTL: 1 hour (3600 seconds)
+- **Configurable**: Set via `CACHE_TTL` environment variable in seconds
 
 ### Seeds & Specific Examples
 Seed files under `mvp-platform-services/vehicles/sql/schema/`:
@@ -81,7 +82,8 @@ Changes:
 - Migrations packaged in image under `/app/migrations/features/[feature]/migrations`.
 - Runner (`backend/src/_system/migrations/run-all.ts`):
   - Reads base dir from `MIGRATIONS_DIR` (env in Dockerfile)
-  - Tracks executed files in `_migrations` (idempotent)
+  - Tracks executed files in `_migrations` table and skips already executed files
+  - **Idempotent at file level**: Safe to re-run migration system multiple times
   - Wait/retry for DB readiness to avoid flapping on cold starts
 - Auto‑migrate on backend container start: `node dist/_system/migrations/run-all.js && npm start`
 - Manual: `make migrate` (runs runner inside the container)