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--- a/skills/backend-dev-guidelines/SKILL.md
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@@ -1,302 +1,342 @@
 ---
 name: backend-dev-guidelines
-description: Comprehensive backend development guide for Node.js/Express/TypeScript microservices. Use when creating routes, controllers, services, repositories, middleware, or working with Express APIs, Prisma database access, Sentry error tracking, Zod validation, unifiedConfig, dependency injection, or async patterns. Covers layered architecture (routes → controllers → services → repositories), BaseController pattern, error handling, performance monitoring, testing strategies, and migration from legacy patterns.
+description: Opinionated backend development standards for Node.js + Express + TypeScript microservices. Covers layered architecture, BaseController pattern, dependency injection, Prisma repositories, Zod validation, unifiedConfig, Sentry error tracking, async safety, and testing discipline.
 ---
 # Backend Development Guidelines
-## Purpose
+**(Node.js · Express · TypeScript · Microservices)**
-Establish consistency and best practices across backend microservices (blog-api, auth-service, notifications-service) using modern Node.js/Express/TypeScript patterns.
+You are a **senior backend engineer** operating production-grade services under strict architectural and reliability constraints.
-## When to Use This Skill
+Your goal is to build **predictable, observable, and maintainable backend systems** using:
-Automatically activates when working on:
+* Layered architecture
- Creating or modifying routes, endpoints, APIs
+* Explicit error boundaries
- Building controllers, services, repositories
+* Strong typing and validation
- Implementing middleware (auth, validation, error handling)
+* Centralized configuration
- Database operations with Prisma
+* First-class observability
- Error tracking with Sentry
+
- Input validation with Zod
+This skill defines **how backend code must be written**, not merely suggestions.
 - Configuration management
 - Backend testing and refactoring
 ---
-## Quick Start
+## 1. Backend Feasibility & Risk Index (BFRI)
-### New Backend Feature Checklist
+Before implementing or modifying a backend feature, assess feasibility.
- [ ] **Route**: Clean definition, delegate to controller
+### BFRI Dimensions (1–5)
 - [ ] **Controller**: Extend BaseController
 - [ ] **Service**: Business logic with DI
 - [ ] **Repository**: Database access (if complex)
 - [ ] **Validation**: Zod schema
 - [ ] **Sentry**: Error tracking
 - [ ] **Tests**: Unit + integration tests
 - [ ] **Config**: Use unifiedConfig
-### New Microservice Checklist
+| Dimension                     | Question                                                         |
 | ----------------------------- | ---------------------------------------------------------------- |
 | **Architectural Fit**         | Does this follow routes → controllers → services → repositories? |
 | **Business Logic Complexity** | How complex is the domain logic?                                 |
 | **Data Risk**                 | Does this affect critical data paths or transactions?            |
 | **Operational Risk**          | Does this impact auth, billing, messaging, or infra?             |
 | **Testability**               | Can this be reliably unit + integration tested?                  |
- [ ] Directory structure (see [architecture-overview.md](architecture-overview.md))
+### Score Formula
- [ ] instrument.ts for Sentry
+
- [ ] unifiedConfig setup
+```
- [ ] BaseController class
+BFRI = (Architectural Fit + Testability) − (Complexity + Data Risk + Operational Risk)
- [ ] Middleware stack
+```
- [ ] Error boundary
+
- [ ] Testing framework
+**Range:** `-10 → +10`
 ### Interpretation
 | BFRI     | Meaning   | Action                 |
 | -------- | --------- | ---------------------- |
 | **6–10** | Safe      | Proceed                |
 | **3–5**  | Moderate  | Add tests + monitoring |
 | **0–2**  | Risky     | Refactor or isolate    |
 | **< 0**  | Dangerous | Redesign before coding |
 ---
-## Architecture Overview
+## 2. When to Use This Skill
-### Layered Architecture
+Automatically applies when working on:
-```
+* Routes, controllers, services, repositories
-HTTP Request
+* Express middleware
-    ↓
+* Prisma database access
-Routes (routing only)
+* Zod validation
-    ↓
+* Sentry error tracking
-Controllers (request handling)
+* Configuration management
-    ↓
+* Backend refactors or migrations
 Services (business logic)
    ↓
 Repositories (data access)
    ↓
 Database (Prisma)
 ```
 **Key Principle:** Each layer has ONE responsibility.
 See [architecture-overview.md](architecture-overview.md) for complete details.
 ---
-## Directory Structure
+## 3. Core Architecture Doctrine (Non-Negotiable)
 ### 1. Layered Architecture Is Mandatory
 ```
-service/src/
+Routes → Controllers → Services → Repositories → Database
-├── config/              # UnifiedConfig
+```
-├── controllers/         # Request handlers
+
 * No layer skipping
 * No cross-layer leakage
 * Each layer has **one responsibility**
 ---
 ### 2. Routes Only Route
 ```ts
 // ❌ NEVER
 router.post('/create', async (req, res) => {
  await prisma.user.create(...);
 });
 // ✅ ALWAYS
 router.post('/create', (req, res) =>
  userController.create(req, res)
 );
 ```
 Routes must contain **zero business logic**.
 ---
 ### 3. Controllers Coordinate, Services Decide
 * Controllers:
  * Parse request
  * Call services
  * Handle response formatting
  * Handle errors via BaseController
 * Services:
  * Contain business rules
  * Are framework-agnostic
  * Use DI
  * Are unit-testable
 ---
 ### 4. All Controllers Extend `BaseController`
 ```ts
 export class UserController extends BaseController {
  async getUser(req: Request, res: Response): Promise<void> {
    try {
      const user = await this.userService.getById(req.params.id);
      this.handleSuccess(res, user);
    } catch (error) {
      this.handleError(error, res, 'getUser');
    }
  }
 }
 ```
 No raw `res.json` calls outside BaseController helpers.
 ---
 ### 5. All Errors Go to Sentry
 ```ts
 catch (error) {
  Sentry.captureException(error);
  throw error;
 }
 ```
 ❌ `console.log`
 ❌ silent failures
 ❌ swallowed errors
 ---
 ### 6. unifiedConfig Is the Only Config Source
 ```ts
 // ❌ NEVER
 process.env.JWT_SECRET;
 // ✅ ALWAYS
 import { config } from '@/config/unifiedConfig';
 config.auth.jwtSecret;
 ```
 ---
 ### 7. Validate All External Input with Zod
 * Request bodies
 * Query params
 * Route params
 * Webhook payloads
 ```ts
 const schema = z.object({
  email: z.string().email(),
 });
 const input = schema.parse(req.body);
 ```
 No validation = bug.
 ---
 ## 4. Directory Structure (Canonical)
 ```
 src/
 ├── config/              # unifiedConfig
 ├── controllers/         # BaseController + controllers
 ├── services/            # Business logic
-├── repositories/        # Data access
+├── repositories/        # Prisma access
-├── routes/              # Route definitions
+├── routes/              # Express routes
-├── middleware/          # Express middleware
+├── middleware/          # Auth, validation, errors
 ├── types/               # TypeScript types
 ├── validators/          # Zod schemas
-├── utils/               # Utilities
+├── types/               # Shared types
-├── tests/               # Tests
+├── utils/               # Helpers
 ├── tests/               # Unit + integration tests
 ├── instrument.ts        # Sentry (FIRST IMPORT)
-├── app.ts               # Express setup
+├── app.ts               # Express app
 └── server.ts            # HTTP server
 ```
-**Naming Conventions:**
+---
- Controllers: `PascalCase` - `UserController.ts`
+
- Services: `camelCase` - `userService.ts`
+## 5. Naming Conventions (Strict)
- Routes: `camelCase + Routes` - `userRoutes.ts`
+
- Repositories: `PascalCase + Repository` - `UserRepository.ts`
+| Layer      | Convention                |
 | ---------- | ------------------------- |
 | Controller | `PascalCaseController.ts` |
 | Service    | `camelCaseService.ts`     |
 | Repository | `PascalCaseRepository.ts` |
 | Routes     | `camelCaseRoutes.ts`      |
 | Validators | `camelCase.schema.ts`     |
 ---
-## Core Principles (7 Key Rules)
+## 6. Dependency Injection Rules
-### 1. Routes Only Route, Controllers Control
+* Services receive dependencies via constructor
 * No importing repositories directly inside controllers
 * Enables mocking and testing
-```typescript
+```ts
-// ❌ NEVER: Business logic in routes
+export class UserService {
-router.post('/submit', async (req, res) => {
+  constructor(
-    // 200 lines of logic
+    private readonly userRepository: UserRepository
-});
+  ) {}
 // ✅ ALWAYS: Delegate to controller
 router.post('/submit', (req, res) => controller.submit(req, res));
 ```
 ### 2. All Controllers Extend BaseController
 ```typescript
 export class UserController extends BaseController {
    async getUser(req: Request, res: Response): Promise<void> {
        try {
            const user = await this.userService.findById(req.params.id);
            this.handleSuccess(res, user);
        } catch (error) {
            this.handleError(error, res, 'getUser');
        }
    }
 }
 ```
-### 3. All Errors to Sentry
+---
-```typescript
+## 7. Prisma & Repository Rules
-try {
+
-    await operation();
+* Prisma client **never used directly in controllers**
-} catch (error) {
+* Repositories:
-    Sentry.captureException(error);
+
-    throw error;
+  * Encapsulate queries
-}
+  * Handle transactions
  * Expose intent-based methods
 ```ts
 await userRepository.findActiveUsers();
 ```
-### 4. Use unifiedConfig, NEVER process.env
+---
-```typescript
+## 8. Async & Error Handling
 // ❌ NEVER
 const timeout = process.env.TIMEOUT_MS;
-// ✅ ALWAYS
+### asyncErrorWrapper Required
-import { config } from './config/unifiedConfig';
+
-const timeout = config.timeouts.default;
+All async route handlers must be wrapped.
 ```ts
 router.get(
  '/users',
  asyncErrorWrapper((req, res) =>
    controller.list(req, res)
  )
 );
 ```
-### 5. Validate All Input with Zod
+No unhandled promise rejections.
-```typescript
+---
 const schema = z.object({ email: z.string().email() });
 const validated = schema.parse(req.body);
 ```
-### 6. Use Repository Pattern for Data Access
+## 9. Observability & Monitoring
-```typescript
+### Required
 // Service → Repository → Database
 const users = await userRepository.findActive();
 ```
-### 7. Comprehensive Testing Required
+* Sentry error tracking
 * Sentry performance tracing
 * Structured logs (where applicable)
-```typescript
+Every critical path must be observable.
 ---
 ## 10. Testing Discipline
 ### Required Tests
 * **Unit tests** for services
 * **Integration tests** for routes
 * **Repository tests** for complex queries
 ```ts
 describe('UserService', () => {
-    it('should create user', async () => {
+  it('creates a user', async () => {
-        expect(user).toBeDefined();
+    expect(user).toBeDefined();
-    });
+  });
 });
 ```
---
+No tests → no merge.
 ## Common Imports
 ```typescript
 // Express
 import express, { Request, Response, NextFunction, Router } from 'express';
 // Validation
 import { z } from 'zod';
 // Database
 import { PrismaClient } from '@prisma/client';
 import type { Prisma } from '@prisma/client';
 // Sentry
 import * as Sentry from '@sentry/node';
 // Config
 import { config } from './config/unifiedConfig';
 // Middleware
 import { SSOMiddlewareClient } from './middleware/SSOMiddleware';
 import { asyncErrorWrapper } from './middleware/errorBoundary';
 ```
 ---
-## Quick Reference
+## 11. Anti-Patterns (Immediate Rejection)
 ### HTTP Status Codes
 | Code | Use Case |
 |------|----------|
 | 200 | Success |
 | 201 | Created |
 | 400 | Bad Request |
 | 401 | Unauthorized |
 | 403 | Forbidden |
 | 404 | Not Found |
 | 500 | Server Error |
 ### Service Templates
 **Blog API** (✅ Mature) - Use as template for REST APIs
 **Auth Service** (✅ Mature) - Use as template for authentication patterns
 ---
 ## Anti-Patterns to Avoid
 ❌ Business logic in routes
-❌ Direct process.env usage
+❌ Skipping service layer
-❌ Missing error handling
+❌ Direct Prisma in controllers
-❌ No input validation
+❌ Missing validation
-❌ Direct Prisma everywhere
+❌ process.env usage
 ❌ console.log instead of Sentry
 ❌ Untested business logic
 ---
-## Navigation Guide
+## 12. Integration With Other Skills
-| Need to... | Read this |
+* **frontend-dev-guidelines** → API contract alignment
-|------------|-----------|
+* **error-tracking** → Sentry standards
-| Understand architecture | [architecture-overview.md](architecture-overview.md) |
+* **database-verification** → Schema correctness
-| Create routes/controllers | [routing-and-controllers.md](routing-and-controllers.md) |
+* **analytics-tracking** → Event pipelines
-| Organize business logic | [services-and-repositories.md](services-and-repositories.md) |
+* **skill-developer** → Skill governance
 | Validate input | [validation-patterns.md](validation-patterns.md) |
 | Add error tracking | [sentry-and-monitoring.md](sentry-and-monitoring.md) |
 | Create middleware | [middleware-guide.md](middleware-guide.md) |
 | Database access | [database-patterns.md](database-patterns.md) |
 | Manage config | [configuration.md](configuration.md) |
 | Handle async/errors | [async-and-errors.md](async-and-errors.md) |
 | Write tests | [testing-guide.md](testing-guide.md) |
 | See examples | [complete-examples.md](complete-examples.md) |
 ---
-## Resource Files
+## 13. Operator Validation Checklist
-### [architecture-overview.md](architecture-overview.md)
+Before finalizing backend work:
 Layered architecture, request lifecycle, separation of concerns
-### [routing-and-controllers.md](routing-and-controllers.md)
+* [ ] BFRI ≥ 3
-Route definitions, BaseController, error handling, examples
+* [ ] Layered architecture respected
-
+* [ ] Input validated
-### [services-and-repositories.md](services-and-repositories.md)
+* [ ] Errors captured in Sentry
-Service patterns, DI, repository pattern, caching
+* [ ] unifiedConfig used
-
+* [ ] Tests written
-### [validation-patterns.md](validation-patterns.md)
+* [ ] No anti-patterns present
 Zod schemas, validation, DTO pattern
 ### [sentry-and-monitoring.md](sentry-and-monitoring.md)
 Sentry init, error capture, performance monitoring
 ### [middleware-guide.md](middleware-guide.md)
 Auth, audit, error boundaries, AsyncLocalStorage
 ### [database-patterns.md](database-patterns.md)
 PrismaService, repositories, transactions, optimization
 ### [configuration.md](configuration.md)
 UnifiedConfig, environment configs, secrets
 ### [async-and-errors.md](async-and-errors.md)
 Async patterns, custom errors, asyncErrorWrapper
 ### [testing-guide.md](testing-guide.md)
 Unit/integration tests, mocking, coverage
 ### [complete-examples.md](complete-examples.md)
 Full examples, refactoring guide
 ---
-## Related Skills
+## 14. Skill Status
 - **database-verification** - Verify column names and schema consistency
 - **error-tracking** - Sentry integration patterns
 - **skill-developer** - Meta-skill for creating and managing skills
 **Status:** Stable · Enforceable · Production-grade
 **Intended Use:** Long-lived Node.js microservices with real traffic and real risk
 ---
 **Skill Status**: COMPLETE ✅
 **Line Count**: < 500 ✅
 **Progressive Disclosure**: 11 resource files ✅