applying-backend-dev-guidelines

name

applying-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.

Backend Development Guidelines

Purpose

Establish consistency and best practices across backend microservices (blog-api, auth-service, notifications-service) using modern Node.js/Express/TypeScript patterns.

When to Use This Skill

Automatically activates when working on:

• Creating or modifying routes, endpoints, APIs
• Building controllers, services, repositories
• Implementing middleware (auth, validation, error handling)
• Database operations with Prisma
• Error tracking with Sentry
• Input validation with Zod
• Configuration management
• Backend testing and refactoring

---

Quick Start

New Backend Feature Checklist

• Route: Clean definition, delegate to controller
• 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

• Directory structure (see architecture-overview.md)
• instrument.ts for Sentry
• unifiedConfig setup
• BaseController class
• Middleware stack
• Error boundary
• Testing framework

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Architecture Overview

Layered Architecture

HTTP Request
    ↓
Routes (routing only)
    ↓
Controllers (request handling)
    ↓
Services (business logic)
    ↓
Repositories (data access)
    ↓
Database (Prisma)

Key Principle: Each layer has ONE responsibility.

See architecture-overview.md for complete details.

---

Directory Structure

service/src/
├── config/              # UnifiedConfig
├── controllers/         # Request handlers
├── services/            # Business logic
├── repositories/        # Data access
├── routes/              # Route definitions
├── middleware/          # Express middleware
├── types/               # TypeScript types
├── validators/          # Zod schemas
├── utils/               # Utilities
├── tests/               # Tests
├── instrument.ts        # Sentry (FIRST IMPORT)
├── app.ts               # Express setup
└── server.ts            # HTTP server

Naming Conventions:

• Controllers: PascalCase - UserController.ts
• Services: camelCase - userService.ts
• Routes: camelCase + Routes - userRoutes.ts
• Repositories: PascalCase + Repository - UserRepository.ts

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Core Principles (7 Key Rules)

1. Routes Only Route, Controllers Control

// ❌ NEVER: Business logic in routes
router.post('/submit', async (req, res) => {
    // 200 lines of logic
});

// ✅ ALWAYS: Delegate to controller
router.post('/submit', (req, res) => controller.submit(req, res));

2. All Controllers Extend BaseController

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

try {
    await operation();
} catch (error) {
    Sentry.captureException(error);
    throw error;
}

4. Use unifiedConfig, NEVER process.env

// ❌ NEVER
const timeout = process.env.TIMEOUT_MS;

// ✅ ALWAYS
import { config } from './config/unifiedConfig';
const timeout = config.timeouts.default;

5. Validate All Input with Zod

const schema = z.object({ email: z.string().email() });
const validated = schema.parse(req.body);

6. Use Repository Pattern for Data Access

// Service → Repository → Database
const users = await userRepository.findActive();

7. Comprehensive Testing Required

describe('UserService', () => {
    it('should create user', async () => {
        expect(user).toBeDefined();
    });
});

---

Common Imports

// 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

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

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Anti-Patterns to Avoid

❌ Business logic in routes ❌ Direct process.env usage ❌ Missing error handling ❌ No input validation ❌ Direct Prisma everywhere ❌ console.log instead of Sentry

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Navigation Guide

Need to...	Read this
Understand architecture	architecture-overview.md
Create routes/controllers	routing-and-controllers.md
Organize business logic	services-and-repositories.md
Validate input	validation-patterns.md
Add error tracking	sentry-and-monitoring.md
Create middleware	middleware-guide.md
Database access	database-patterns.md
Manage config	configuration.md
Handle async/errors	async-and-errors.md
Write tests	testing-guide.md
See examples	complete-examples.md

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Resource Files

architecture-overview.md

Layered architecture, request lifecycle, separation of concerns

routing-and-controllers.md

Route definitions, BaseController, error handling, examples

services-and-repositories.md

Service patterns, DI, repository pattern, caching

validation-patterns.md

Zod schemas, validation, DTO pattern

sentry-and-monitoring.md

Sentry init, error capture, performance monitoring

middleware-guide.md

Auth, audit, error boundaries, AsyncLocalStorage

database-patterns.md

PrismaService, repositories, transactions, optimization

configuration.md

UnifiedConfig, environment configs, secrets

async-and-errors.md

Async patterns, custom errors, asyncErrorWrapper

testing-guide.md

Unit/integration tests, mocking, coverage

complete-examples.md

Full examples, refactoring guide

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Related Skills

• database-verification - Verify column names and schema consistency
• error-tracking - Sentry integration patterns
• skill-developer - Meta-skill for creating and managing skills

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Skill Status: COMPLETE ✅ Line Count: < 500 ✅ Progressive Disclosure: 11 resource files ✅