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name backend description Backend development with Node.js, Express, NestJS, and server patterns domain development-stacks version 1.0.0 tags ["nodejs","express","nestjs","fastify","api","middleware","authentication"] triggers {"keywords":{"primary":["backend","server","nodejs","express","nestjs","api","microservice"],"secondary":["fastify","middleware","authentication","rest","graphql","queue"]},"context_boost":["service","endpoint","database","http"],"context_penalty":["frontend","css","ui","mobile"],"priority":"high"} collaboration {"prerequisites":[{"skill":"typescript","reason":"Type-safe backend development"}],"delegation_triggers":[{"trigger":"API endpoint design decisions","delegate_to":"api-design","context":"RESTful conventions, versioning, error formats"},{"trigger":"Database schema design or query optimization","delegate_to":"database","context":"Data modeling, indexing strategy"},{"trigger":"Writing tests for services or controllers","delegate_to":"testing-strategies","context":"Integration test patterns, mocking strategies"}],"receives_context_from":[{"skill":"api-design","receives":["Endpoint naming conventions","Request/response formats","Error response structure"]},{"skill":"database","receives":["Connection pool settings","Query optimization hints","Transaction patterns"]}],"provides_context_to":[{"skill":"frontend","provides":["API endpoints list","Authentication flow","WebSocket events"]},{"skill":"testing-strategies","provides":["Service dependencies to mock","Integration test scenarios"]}]}
Backend Development
Overview
Server-side development patterns, frameworks, and best practices for building scalable APIs and services.
Express.js
Application Structure
import express from 'express' ;
import helmet from 'helmet' ;
import cors from 'cors' ;
import compression from 'compression' ;
import { errorHandler } from './middleware/errorHandler' ;
import { requestLogger } from './middleware/requestLogger' ;
import routes from './routes' ;
const app = express ();
app.use (helmet ());
app.use (cors ({
origin : process.env .ALLOWED_ORIGINS ?.split (',' ) || '*' ,
credentials : true ,
}));
app.use (compression ());
app.use (express.json ({ limit : '10kb' }));
app.use (express.urlencoded ({ extended : }));
app. (requestLogger);
app. ( , routes);
app. ( , {
res. ({ : , : (). () });
});
app. (errorHandler);
app;
true
use
use
'/api/v1'
get
'/health'
(req, res ) =>
json
status
'healthy'
timestamp
new
Date
toISOString
use
export
default
Middleware Patterns
import { Request , Response , NextFunction } from 'express' ;
import jwt from 'jsonwebtoken' ;
interface AuthRequest extends Request {
user ?: { id : string ; role : string };
}
export function authenticate (req : AuthRequest , res : Response , next : NextFunction ) {
const token = req.headers .authorization ?.replace ('Bearer ' , '' );
if (!token) {
return res.status (401 ).json ({ error : 'Authentication required' });
}
try {
const decoded = jwt.verify (token, process.env .JWT_SECRET !) as { id : string ; role : string };
req.user = decoded;
next ();
} catch {
return res.status (401 ).json ({ error : 'Invalid token' });
}
}
export function authorize (...roles : string [] ) {
return (req : AuthRequest , res : Response , next : NextFunction ) => {
if (!req.user || !roles.includes (req.user .role )) {
return res.status (403 ).json ({ error : 'Forbidden' });
}
next ();
};
}
import rateLimit from 'express-rate-limit' ;
export const apiLimiter = rateLimit ({
windowMs : 15 * 60 * 1000 ,
max : 100 ,
message : { error : 'Too many requests' },
standardHeaders : true ,
});
import { z } from 'zod' ;
export function validate (schema : z.ZodSchema ) {
return (req : Request , res : Response , next : NextFunction ) => {
const result = schema.safeParse ({
body : req.body ,
query : req.query ,
params : req.params ,
});
if (!result.success ) {
return res.status (400 ).json ({
error : 'Validation failed' ,
details : result.error .flatten (),
});
}
req.body = result.data .body ;
req.query = result.data .query ;
req.params = result.data .params ;
next ();
};
}
Error Handling
export class AppError extends Error {
constructor (
public statusCode : number ,
public message : string ,
public isOperational = true
) {
super (message);
Error .captureStackTrace (this , this .constructor );
}
}
export class NotFoundError extends AppError {
constructor (resource : string ) {
super (404 , `${resource} not found` );
}
}
export class ValidationError extends AppError {
constructor (message : string ) {
super (400 , message);
}
}
export function errorHandler (
err : Error ,
req : Request ,
res : Response ,
next : NextFunction
) {
console .error ('Error:' , err);
if (err instanceof AppError ) {
return res.status (err.statusCode ).json ({
error : err.message ,
...(process.env .NODE_ENV === 'development' && { stack : err.stack }),
});
}
if (err.name === 'CastError' ) {
return res.status (400 ).json ({ error : 'Invalid ID format' });
}
if (err.name === 'ValidationError' ) {
return res.status (400 ).json ({ error : err.message });
}
res.status (500 ).json ({
error : process.env .NODE_ENV === 'production'
? 'Internal server error'
: err.message ,
});
}
NestJS
Module Structure
import { Module } from '@nestjs/common' ;
import { UsersController } from './users.controller' ;
import { UsersService } from './users.service' ;
import { PrismaModule } from '../prisma/prisma.module' ;
@Module ({
imports : [PrismaModule ],
controllers : [UsersController ],
providers : [UsersService ],
exports : [UsersService ],
})
export class UsersModule {}
import {
Controller , Get , Post , Put , Delete ,
Body , Param , Query , UseGuards ,
HttpCode , HttpStatus ,
} from '@nestjs/common' ;
import { ApiTags , ApiOperation , ApiBearerAuth } from '@nestjs/swagger' ;
import { UsersService } from './users.service' ;
import { CreateUserDto , UpdateUserDto , QueryUsersDto } from './dto' ;
import { JwtAuthGuard } from '../auth/guards/jwt-auth.guard' ;
import { RolesGuard } from '../auth/guards/roles.guard' ;
import { Roles } from '../auth/decorators/roles.decorator' ;
@ApiTags ('users' )
@Controller ('users' )
@UseGuards (JwtAuthGuard , RolesGuard )
@ApiBearerAuth ()
export class UsersController {
constructor (private readonly usersService : UsersService ) {}
@Get ()
@ApiOperation ({ summary : 'List users' })
async findAll (@Query () query : QueryUsersDto ) {
return this .usersService .findAll (query);
}
@Get (':id' )
@ApiOperation ({ summary : 'Get user by ID' })
async findOne (@Param ('id' ) id : string ) {
return this .usersService .findOne (id);
}
@Post ()
@Roles ('admin' )
@ApiOperation ({ summary : 'Create user' })
async create (@Body () createUserDto : CreateUserDto ) {
return this .usersService .create (createUserDto);
}
@Put (':id' )
@ApiOperation ({ summary : 'Update user' })
async update (@Param ('id' ) id : string , @Body () updateUserDto : UpdateUserDto ) {
return this .usersService .update (id, updateUserDto);
}
@Delete (':id' )
@Roles ('admin' )
@HttpCode (HttpStatus .NO_CONTENT )
@ApiOperation ({ summary : 'Delete user' })
async remove (@Param ('id' ) id : string ) {
await this .usersService .remove (id);
}
}
DTOs with Validation
import { IsEmail , IsString , MinLength , IsOptional , IsEnum } from 'class-validator' ;
import { ApiProperty , ApiPropertyOptional } from '@nestjs/swagger' ;
export enum UserRole {
USER = 'user' ,
ADMIN = 'admin' ,
}
export class CreateUserDto {
@ApiProperty ({ example : 'user@example.com' })
@IsEmail ()
email : string ;
@ApiProperty ({ minLength : 8 })
@IsString ()
@MinLength (8 )
password : string ;
@ApiPropertyOptional ()
@IsOptional ()
@IsString ()
name ?: string ;
@ApiPropertyOptional ({ enum : UserRole , default : UserRole .USER })
@IsOptional ()
@IsEnum (UserRole )
role ?: UserRole = UserRole .USER ;
}
import { PartialType , OmitType } from '@nestjs/swagger' ;
export class UpdateUserDto extends PartialType (
OmitType (CreateUserDto , ['password' ] as const )
) {}
Services with Dependency Injection
import { Injectable , NotFoundException } from '@nestjs/common' ;
import { PrismaService } from '../prisma/prisma.service' ;
import { CreateUserDto , UpdateUserDto , QueryUsersDto } from './dto' ;
import * as argon2 from 'argon2' ;
@Injectable ()
export class UsersService {
constructor (private prisma : PrismaService ) {}
async findAll (query : QueryUsersDto ) {
const { page = 1 , limit = 10 , search } = query;
const where = search
? {
OR : [
{ name : { contains : search, mode : 'insensitive' } },
{ email : { contains : search, mode : 'insensitive' } },
],
}
: {};
const [users, total] = await Promise .all ([
this .prisma .user .findMany ({
where,
skip : (page - 1 ) * limit,
take : limit,
select : {
id : true ,
email : true ,
name : true ,
role : true ,
createdAt : true ,
},
}),
this .prisma .user .count ({ where }),
]);
return {
data : users,
meta : {
page,
limit,
total,
totalPages : Math .ceil (total / limit),
},
};
}
async findOne (id : string ) {
const user = await this .prisma .user .findUnique ({
where : { id },
select : {
id : true ,
email : true ,
name : true ,
role : true ,
createdAt : true ,
},
});
if (!user) {
throw new NotFoundException (`User with ID ${id} not found` );
}
return user;
}
async create (dto : CreateUserDto ) {
const hashedPassword = await argon2.hash (dto.password );
return this .prisma .user .create ({
data : {
...dto,
password : hashedPassword,
},
select : {
id : true ,
email : true ,
name : true ,
role : true ,
},
});
}
async update (id : string , dto : UpdateUserDto ) {
await this .findOne (id);
return this .prisma .user .update ({
where : { id },
data : dto,
select : {
id : true ,
email : true ,
name : true ,
role : true ,
},
});
}
async remove (id : string ) {
await this .findOne (id);
await this .prisma .user .delete ({ where : { id } });
}
}
Database Integration
Prisma ORM
generator client {
provider = "prisma-client-js"
}
datasource db {
provider = "postgresql"
url = env ("DATABASE_URL" )
}
model User {
id String @id @default (cuid ())
email String @unique
password String
name String ?
role Role @default (USER )
posts Post []
createdAt DateTime @default (now ())
updatedAt DateTime @updatedAt
}
model Post {
id String @id @default (cuid ())
title String
content String ?
published Boolean @default (false )
author User @relation (fields : [authorId], references : [id])
authorId String
createdAt DateTime @default (now ())
updatedAt DateTime @updatedAt
}
enum Role {
USER
ADMIN
}
import { Injectable , OnModuleInit , OnModuleDestroy } from '@nestjs/common' ;
import { PrismaClient } from '@prisma/client' ;
@Injectable ()
export class PrismaService extends PrismaClient implements OnModuleInit , OnModuleDestroy {
async onModuleInit ( ) {
await this .$connect();
}
async onModuleDestroy ( ) {
await this .$disconnect();
}
}
Transactions
async transferFunds (fromId : string , toId : string , amount : number ) {
return this .prisma .$transaction(async (tx) => {
const from = await tx.account .update ({
where : { id : fromId },
data : { balance : { decrement : amount } },
});
if (from .balance < 0 ) {
throw new Error ('Insufficient funds' );
}
const to = await tx.account .update ({
where : { id : toId },
data : { balance : { increment : amount } },
});
await tx.transfer .create ({
data : {
fromId,
toId,
amount,
},
});
return { from , to };
});
}
Background Jobs
Bull Queue
import { Process , Processor } from '@nestjs/bull' ;
import { Job } from 'bull' ;
import { MailService } from '../mail/mail.service' ;
@Processor ('email' )
export class EmailProcessor {
constructor (private mailService : MailService ) {}
@Process ('welcome' )
async handleWelcomeEmail (job : Job <{ email: string ; name: string }> ) {
const { email, name } = job.data ;
await this .mailService .sendWelcome (email, name);
}
@Process ('password-reset' )
async handlePasswordReset (job : Job <{ email: string ; token: string }> ) {
const { email, token } = job.data ;
await this .mailService .sendPasswordReset (email, token);
}
}
import { InjectQueue } from '@nestjs/bull' ;
import { Queue } from 'bull' ;
@Injectable ()
export class UsersService {
constructor (@InjectQueue ('email' ) private emailQueue : Queue ) {}
async createUser (dto : CreateUserDto ) {
const user = await this .prisma .user .create ({ data : dto });
await this .emailQueue .add ('welcome' , {
email : user.email ,
name : user.name ,
});
return user;
}
}
WebSockets
import {
WebSocketGateway ,
WebSocketServer ,
SubscribeMessage ,
OnGatewayConnection ,
OnGatewayDisconnect ,
} from '@nestjs/websockets' ;
import { Server , Socket } from 'socket.io' ;
@WebSocketGateway ({
cors : { origin : '*' },
namespace : '/events' ,
})
export class EventsGateway implements OnGatewayConnection , OnGatewayDisconnect {
@WebSocketServer ()
server : Server ;
handleConnection (client : Socket ) {
console .log (`Client connected: ${client.id} ` );
}
handleDisconnect (client : Socket ) {
console .log (`Client disconnected: ${client.id} ` );
}
@SubscribeMessage ('join-room' )
handleJoinRoom (client : Socket , room : string ) {
client.join (room);
this .server .to (room).emit ('user-joined' , { userId : client.id });
}
@SubscribeMessage ('message' )
handleMessage (client : Socket , payload : { room: string ; message: string } ) {
this .server .to (payload.room ).emit ('message' , {
userId : client.id ,
message : payload.message ,
timestamp : new Date (),
});
}
broadcastToRoom (room : string , event : string , data : any ) {
this .server .to (room).emit (event, data);
}
}
Related Skills
[[api-design]] - API design patterns
[[database]] - Database patterns
[[security-practices]] - Backend security
Sharp Edges(常見陷阱)
SE-1: 未處理的 Promise Rejection
嚴重度 : critical
情境 : Async 函數中的錯誤沒有被 catch,導致應用程式崩潰或無聲失敗
原因 : 忘記 await、沒有錯誤處理、或在 callback 中使用 async
症狀 :
UnhandledPromiseRejectionWarning
API 請求 hang 住不回應
資料庫操作部分完成
檢測 : \.then\([^)]*\)(?!\s*\.catch)|async.*(?<!await\s)db\.|async.*(?<!await\s)fetch
解法 : 使用 try-catch 包裝、加上 global error handler、使用 ESLint no-floating-promises 規則
SE-2: N+1 查詢問題
嚴重度 : high
情境 : 在迴圈中執行資料庫查詢,導致效能急劇下降
原因 : ORM 的 lazy loading、沒有使用 batch fetch
症狀 :
查詢數量與資料量成正比
API 響應時間隨資料量線性增長
資料庫連接池耗盡
檢測 : for.*await.*findOne|forEach.*await.*find|\.map\(.*await.*query
解法 : 使用 eager loading (include/populate)、DataLoader、批次查詢
SE-3: 敏感資訊洩露
嚴重度 : critical
情境 : 錯誤訊息、日誌、或 API 回應中包含敏感資訊
原因 : 開發環境的 debug 設定被帶到生產、錯誤處理過於詳細
症狀 :
錯誤回應包含 stack trace
日誌中有密碼或 token
API 回應包含內部資料庫結構
檢測 : console\.log.*password|console\.log.*token|res\.json\(err\)|stack.*trace
解法 : 生產環境只回傳通用錯誤訊息、使用專門的錯誤序列化、過濾敏感欄位
SE-4: 競態條件 (Race Condition)
嚴重度 : high
情境 : 多個請求同時修改同一資源,導致資料不一致
原因 : 缺乏適當的鎖定機制、read-modify-write 沒有原子性
症狀 :
庫存數量變成負數
重複扣款
資料覆蓋(後來的寫入覆蓋先前的)
檢測 : findOne.*update|get.*set|read.*write
解法 : 使用資料庫事務、樂觀鎖 (version field)、分散式鎖
SE-5: 未驗證的用戶輸入
嚴重度 : critical
情境 : 直接使用用戶輸入進行資料庫查詢或系統命令
原因 : 信任前端驗證、沒有後端驗證、拼接 SQL/命令字串
症狀 :
SQL Injection 攻擊
NoSQL Injection
Command Injection
檢測 : \$\{.*req\.body|query\(.*\+.*req\.|exec\(.*req\.|eval\(
解法 : 使用參數化查詢、輸入驗證(Zod/Joi)、白名單驗證
Validations
V-1: 禁止空的 catch block
類型 : regex
嚴重度 : critical
模式 : catch\s*\([^)]*\)\s*\{\s*\}
訊息 : Empty catch block silently swallows errors
修復建議 : Add error logging: console.error(err) or logger.error(err)
適用 : *.ts, *.js
V-2: 禁止 forEach + async
類型 : regex
嚴重度 : high
模式 : \.forEach\s*\(\s*async
訊息 : forEach does not await async callbacks - use for...of or Promise.all
修復建議 : Replace with for (const item of items) or await Promise.all(items.map(...))
適用 : *.ts, *.js
V-3: 檢測未處理的 Promise
類型 : regex
嚴重度 : high
模式 : (?<!await\s)(?<!return\s)(?<!\.\s*catch\()fetch\(|db\.(find|query|insert|update|delete)
訊息 : Async operation may not be awaited or caught
修復建議 : Add await keyword or .catch() handler
適用 : *.ts, *.js
V-4: 禁止硬編碼密鑰
類型 : regex
嚴重度 : critical
模式 : (password|secret|api_key|apikey|token)\s*[=:]\s*["'][^"']+["']
訊息 : Hardcoded secret detected - use environment variables
修復建議 : Move to environment variables: process.env.SECRET_KEY
適用 : *.ts, *.js, *.json
V-5: 禁止 SELECT *
類型 : regex
嚴重度 : medium
模式 : SELECT\s+\*\s+FROM|\.findMany\s*\(\s*\)|\.find\s*\(\s*\{\s*\}\s*\)
訊息 : SELECT * fetches unnecessary data - specify fields
修復建議 : Explicitly list needed fields: SELECT id, name FROM...
適用 : *.ts, *.js, *.sql