docs: sync from backend cab0719 - align request budget validation

01 - Architecture/Backend Architecture.md

@@ -6,10 +6,10 @@ created: 2026-05-23
 
 # Backend Architecture
 
-Module-level architecture of the Express 5 + TypeScript + Mongoose backend at `/Users/mojtabaheidari/code/backend` (development branch).
+Module-level architecture of the Express 5 + TypeScript backend. MongoDB/Mongoose is still the primary runtime persistence layer; the `integrate-main-into-development` backend also contains the Drizzle/Postgres migration layer.
 
 > [!info]
-> Repo: `git@git.manko.yoga:222/nick/backend.git` · Branch: `development` · Version: 2.6.3-beta (`package.json:4`)
+> Repo: `git@git.manko.yoga:222/nick/backend.git` · Active integration branch: `integrate-main-into-development` · Current baseline: backend `2.6.79` at `3a50dc4`
 
 ---
 
@@ -24,6 +24,7 @@ backend/src/
 │   ├── database/               # Mongoose connection, retries, graceful shutdown
 │   └── socket/socketService.ts # Socket.IO server, rooms, emit helpers
 ├── models/                     # Mongoose models — see 02 - Data Models/
+├── db/                         # Drizzle/Postgres migration layer: schemas, migrations, repos, backfill, verify
 ├── routes/                     # Express Router definitions (mounted in app.ts)
 ├── scripts/                    # CLI utilities (seed:users, seed:categories, ...)
 ├── seeds/                      # Seed data fixtures
@@ -60,6 +61,9 @@ backend/src/
 └── utils/                      # Pure utility fns (logger, currencyUtils, etc.)
 ```
 
+> [!warning] Postgres is not the default runtime store yet
+> `src/db/repositories/factory.ts` can select `mongo`, `dual`, or `pg` implementations for user, payment, points, and marketplace domains, but the broad service layer still imports Mongoose models directly. A code scan on 2026-05-31 found no runtime calls to `createRepositories()` / `getPaymentRepo()` / `getMarketplaceRepo()` outside the factory itself. See [[Postgres Runtime Cutover Status]] before assuming a `REPO_*` flag changes live behavior.
+
 > [!tip]
 > Service folders are self-contained: each typically has `<feature>Service.ts`, `<feature>Controller.ts`, `<feature>Routes.ts`, `<feature>Validation.ts`. This makes each service movable to a microservice later with minimal coupling.
 
@@ -82,7 +86,7 @@ The bootstrap is intentionally linear and easy to audit. Execution order:
 11. **Error handler** — central `errorHandler` middleware formats responses via `response-handler.ts`.
 12. **HTTP server creation** — `const server = http.createServer(app)`.
 13. **Socket.IO attach** — `initSocket(server, corsOptions)` (see [[Real-time Layer]]).
-14. **DB connect** — `await connectDatabase()`.
+14. **DB connect** — `await connectDatabase()` for MongoDB/Mongoose. Postgres connects lazily only when PG modules are imported (for example oracle quote persistence with `ORACLE_QUOTING_ENABLED=true`) and requires `PG_URL`.
 15. **Redis connect** — `await connectRedis()`.
 16. **Listen** — `server.listen(config.port, ...)`.
 17. **Graceful shutdown** — SIGTERM/SIGINT handlers close server, drain sockets, close Mongoose, close Redis.