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nodejs-backend-patterns
Build production-ready Node.js backend services with
# Node.js Backend Patterns
Comprehensive guidance for building scalable, maintainable, and production-ready Node.js backend applications with modern frameworks, architectural patterns, and best practices.
## When to Use This Skill
- Building REST APIs or GraphQL servers
- Creating microservices with Node.js
- Implementing authentication and authorization
- Designing scalable backend architectures
- Setting up middleware and error handling
- Integrating databases (SQL and NoSQL)
- Building real-time applications with WebSockets
- Implementing background job processing
## Core Frameworks
### Express.js - Minimalist Framework
**Basic Setup:**
```typescript
import express, { Request, Response, NextFunction } from "express";
import helmet from "helmet";
import cors from "cors";
import compression from "compression";
const app = express();
// Security middleware
app.use(helmet());
app.use(cors({ origin: process.env.ALLOWED_ORIGINS?.split(",") }));
app.use(compression());
// Body parsing
app.use(express.json({ limit: "10mb" }));
app.use(express.urlencoded({ extended: true, limit: "10mb" }));
// Request logging
app.use((req: Request, res: Response, next: NextFunction) => {
console.log(`${req.method} ${req.path}`);
next();
});
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
console.log(`Server running on port ${PORT}`);
});
```
### Fastify - High Performance Framework
**Basic Setup:**
```typescript
import Fastify from "fastify";
import helmet from "@fastify/helmet";
import cors from "@fastify/cors";
import compress from "@fastify/compress";
const fastify = Fastify({
logger: {
level: process.env.LOG_LEVEL || "info",
transport: {
target: "pino-pretty",
options: { colorize: true },
},
},
});
// Plugins
await fastify.register(helmet);
await fastify.register(cors, { origin: true });
await fastify.register(compress);
// Type-safe routes with schema validation
fastify.post<{
Body: { name: string; email: string };
Reply: { id: string; name: string };
}>(
"/users",
{
schema: {
body: {
type: "object",
required: ["name", "email"],
properties: {
name: { type: "string", minLength: 1 },
email: { type: "string", format: "email" },
},
},
},
},
async (request, reply) => {
const { name, email } = request.body;
return { id: "123", name };
},
);
await fastify.listen({ port: 3000, host: "0.0.0.0" });
```
## Architectural Patterns
### Pattern 1: Layered Architecture
**Structure:**
```
src/
βββ controllers/ # Handle HTTP requests/responses
βββ services/ # Business logic
βββ repositories/ # Data access layer
βββ models/ # Data models
βββ middleware/ # Express/Fastify middleware
βββ routes/ # Route definitions
βββ utils/ # Helper functions
βββ config/ # Configuration
βββ types/ # TypeScript types
```
**Controller Layer:**
```typescript
// controllers/user.controller.ts
import { Request, Response, NextFunction } from "express";
import { UserService } from "../services/user.service";
import { CreateUserDTO, UpdateUserDTO } from "../types/user.types";
export class UserController {
constructor(private userService: UserService) {}
async createUser(req: Request, res: Response, next: NextFunction) {
try {
const userData: CreateUserDTO = req.body;
const user = await this.userService.createUser(userData);
res.status(201).json(user);
} catch (error) {
next(error);
}
}
async getUser(req: Request, res: Response, next: NextFunction) {
try {
const { id } = req.params;
const user = await this.userService.getUserById(id);
res.json(user);
} catch (error) {
next(error);
}
}
async updateUser(req: Request, res: Response, next: NextFunction) {
try {
const { id } = req.params;
const updates: UpdateUserDTO = req.body;
const user = await this.userService.updateUser(id, updates);
res.json(user);
} catch (error) {
next(error);
}
}
async deleteUser(req: Request, res: Response, next: NextFunction) {
try {
const { id } = req.params;
await this.userService.deleteUser(id);
res.status(204).send();
} catch (error) {
next(error);
}
}
}
```
**Service Layer:**
```typescript
// services/user.service.ts
import { UserRepository } from "../repositories/user.repository";
import { CreateUserDTO, UpdateUserDTO, User } from "../types/user.types";
import { NotFoundError, ValidationError } from "../utils/errors";
import bcrypt from "bcrypt";
export class UserService {
constructor(private userRepository: UserRepository) {}
async createUser(userData: CreateUserDTO): Promise<User> {
// Validation
const existingUser = await this.userRepository.findByEmail(userData.email);
if (existingUser) {
throw new ValidationError("Email already exists");
}
// Hash password
const hashedPassword = await bcrypt.hash(userData.password, 10);
// Create user
const user = await this.userRepository.create({
...userData,
password: hashedPassword,
});
// Remove password from response
const { password, ...userWithoutPassword } = user;
return userWithoutPassword as User;
}
async getUserById(id: string): Promise<User> {
const user = await this.userRepository.findById(id);
if (!user) {
throw new NotFoundError("User not found");
}
const { password, ...userWithoutPassword } = user;
return userWithoutPassword as User;
}
async updateUser(id: string, updates: UpdateUserDTO): Promise<User> {
const user = await this.userRepository.update(id, updates);
if (!user) {
throw new NotFoundError("User not found");
}
const { password, ...userWithoutPassword } = user;
return userWithoutPassword as User;
}
async deleteUser(id: string): Promise<void> {
const deleted = await this.userRepository.delete(id);
if (!deleted) {
throw new NotFoundError("User not found");
}
}
}
```
**Repository Layer:**
```typescript
// repositories/user.repository.ts
import { Pool } from "pg";
import { CreateUserDTO, UpdateUserDTO, UserEntity } from "../types/user.types";
export class UserRepository {
constructor(private db: Pool) {}
async create(
userData: CreateUserDTO & { password: string },
): Promise<UserEntity> {
const query = `
INSERT INTO users (name, email, password)
VALUES ($1, $2, $3)
RETURNING id, name, email, password, created_at, updated_at
`;
const { rows } = await this.db.query(query, [
userData.name,
userData.email,
userData.password,
]);
return rows[0];
}
async findById(id: string): Promise<UserEntity | null> {
const query = "SELECT * FROM users WHERE id = $1";
const { rows } = await this.db.query(query, [id]);
return rows[0] || null;
}
async findByEmail(email: string): Promise<UserEntity | null> {
const query = "SELECT * FROM users WHERE email = $1";
const { rows } = await this.db.query(query, [email]);
return rows[0] || null;
}
async update(id: string, updates: UpdateUserDTO): Promise<UserEntity | null> {
const fields = Object.keys(updates);
const values = Object.values(updates);
const setClause = fields
.map((field, idx) => `${field} = $${idx + 2}`)
.join(", ");
const query = `
UPDATE users
SET ${setClause}, updated_at = CURRENT_TIMESTAMP
WHERE id = $1
RETURNING *
`;
const { rows } = await this.db.query(query, [id, ...values]);
return rows[0] || null;
}
async delete(id: string): Promise<boolean> {
const query = "DELETE FROM users WHERE id = $1";
const { rowCount } = await this.db.query(query, [id]);
return rowCount > 0;
}
}
```
### Pattern 2: Dependency Injection
**DI Container:**
```typescript
// di-container.ts
import { Pool } from "pg";
import { UserRepository } from "./repositories/user.repository";
import { UserService } from "./services/user.service";
import { UserController } from "./controllers/user.controller";
import { AuthService } from "./services/auth.service";
class Container {
private instances = new Map<string, any>();
register<T>(key: string, factory: () => T): void {
this.instances.set(key, factory);
}
resolve<T>(key: string): T {
const factory = this.instances.get(key);
if (!factory) {
throw new Error(`No factory registered for ${key}`);
}
return factory();
}
singleton<T>(key: string, factory: () => T): void {
let instance: T;
this.instances.set(key, () => {
if (!instance) {
instance = factory();
}
return instance;
});
}
}
export const container = new Container();
// Register dependencies
container.singleton(
"db",
() =>
new Pool({
host: process.env.DB_HOST,
port: parseInt(process.env.DB_PORT || "5432"),
database: process.env.DB_NAME,
user: process.env.DB_USER,
password: process.env.DB_PASSWORD,
max: 20,
idleTimeoutMillis: 30000,
connectionTimeoutMillis: 2000,
}),
);
container.singleton(
"userRepository",
() => new UserRepository(container.resolve("db")),
);
container.singleton(
"userService",
() => new UserService(container.resolve("userRepository")),
);
container.register(
"userController",
() => new UserController(container.resolve("userService")),
);
container.singleton(
"authService",
() => new AuthService(container.resolve("userRepository")),
);
```
## Middleware Patterns
### Authentication Middleware
```typescript
// middleware/auth.middleware.ts
import { Request, Response, NextFunction } from "express";
import jwt from "jsonwebtoken";
import { UnauthorizedError } from "../utils/errors";
interface JWTPayload {
userId: string;
email: string;
}
declare global {
namespace Express {
interface Request {
user?: JWTPayload;
}
}
}
export const authenticate = async (
req: Request,
res: Response,
next: NextFunction,
) => {
try {
const token = req.headers.authorization?.replace("Bearer ", "");
if (!token) {
throw new UnauthorizedError("No token provided");
}
const payload = jwt.verify(token, process.env.JWT_SECRET!) as JWTPayload;
req.user = payload;
next();
} catch (error) {
next(new UnauthorizedError("Invalid token"));
}
};
export const authorize = (...roles: string[]) => {
return async (req: Request, res: Response, next: NextFunction) => {
if (!req.user) {
return next(new UnauthorizedError("Not authenticated"));
}
// Check if user has required role
const hasRole = roles.some((role) => req.user?.roles?.includes(role));
if (!hasRole) {
return next(new UnauthorizedError("Insufficient permissions"));
}
next();
};
};
```
### Validation Middleware
```typescript
// middleware/validation.middleware.ts
import { Request, Response, NextFunction } from "express";
import { AnyZodObject, ZodError } from "zod";
import { ValidationError } from "../utils/errors";
export const validate = (schema: AnyZodObject) => {
return async (req: Request, res: Response, next: NextFunction) => {
try {
await schema.parseAsync({
body: req.body,
query: req.query,
params: req.params,
});
next();
} catch (error) {
if (error instanceof ZodError) {
const errors = error.errors.map((err) => ({
field: err.path.join("."),
message: err.message,
}));
next(new ValidationError("Validation failed", errors));
} else {
next(error);
}
}
};
};
// Usage with Zod
import { z } from "zod";
const createUserSchema = z.object({
body: z.object({
name: z.string().min(1),
email: z.string().email(),
password: z.string().min(8),
}),
});
router.post("/users", validate(createUserSchema), userController.createUser);
```
### Rate Limiting Middleware
```typescript
// middleware/rate-limit.middleware.ts
import rateLimit from "express-rate-limit";
import RedisStore from "rate-limit-redis";
import Redis from "ioredis";
const redis = new Redis({
host: process.env.REDIS_HOST,
port: parseInt(process.env.REDIS_PORT || "6379"),
});
export const apiLimiter = rateLimit({
store: new RedisStore({
client: redis,
prefix: "rl:",
}),
windowMs: 15 * 60 * 1000, // 15 minutes
max: 100, // Limit each IP to 100 requests per windowMs
message: "Too many requests from this IP, please try again later",
standardHeaders: true,
legacyHeaders: false,
});
export const authLimiter = rateLimit({
store: new RedisStore({
client: redis,
prefix: "rl:auth:",
}),
windowMs: 15 * 60 * 1000,
max: 5, // Stricter limit for auth endpoints
skipSuccessfulRequests: true,
});
```
### Request Logging Middleware
```typescript
// middleware/logger.middleware.ts
import { Request, Response, NextFunction } from "express";
import pino from "pino";
const logger = pino({
level: process.env.LOG_LEVEL || "info",
transport: {
target: "pino-pretty",
options: { colorize: true },
},
});
export const requestLogger = (
req: Request,
res: Response,
next: NextFunction,
) => {
const start = Date.now();
// Log response when finished
res.on("finish", () => {
const duration = Date.now() - start;
logger.info({
method: req.method,
url: req.url,
status: res.statusCode,
duration: `${duration}ms`,
userAgent: req.headers["user-agent"],
ip: req.ip,
});
});
next();
};
export { logger };
```
## Error Handling
### Custom Error Classes
```typescript
// utils/errors.ts
export class AppError extends Error {
constructor(
public message: string,
public statusCode: number = 500,
public isOperational: boolean = true,
) {
super(message);
Object.setPrototypeOf(this, AppError.prototype);
Error.captureStackTrace(this, this.constructor);
}
}
export class ValidationError extends AppError {
constructor(
message: string,
public errors?: any[],
) {
super(message, 400);
}
}
export class NotFoundError extends AppError {
constructor(message: string = "Resource not found") {
super(message, 404);
}
}
export class UnauthorizedError extends AppError {
constructor(message: string = "Unauthorized") {
super(message, 401);
}
}
export class ForbiddenError extends AppError {
constructor(message: string = "Forbidden") {
super(message, 403);
}
}
export class ConflictError extends AppError {
constructor(message: string) {
super(message, 409);
}
}
```
### Global Error Handler
```typescript
// middleware/error-handler.ts
import { Request, Response, NextFunction } from "express";
import { AppError } from "../utils/errors";
import { logger } from "./logger.middleware";
export const errorHandler = (
err: Error,
req: Request,
res: Response,
next: NextFunction,
) => {
if (err instanceof AppError) {
return res.status(err.statusCode).json({
status: "error",
message: err.message,
...(err instanceof ValidationError && { errors: err.errors }),
});
}
// Log unexpected errors
logger.error({
error: err.message,
stack: err.stack,
url: req.url,
method: req.method,
});
// Don't leak error details in production
const message =
process.env.NODE_ENV === "production"
? "Internal server error"
: err.message;
res.status(500).json({
status: "error",
message,
});
};
// Async error wrapper
export const asyncHandler = (
fn: (req: Request, res: Response, next: NextFunction) => Promise<any>,
) => {
return (req: Request, res: Response, next: NextFunction) => {
Promise.resolve(fn(req, res, next)).catch(next);
};
};
```
## Database Patterns
### PostgreSQL with Connection Pool
```typescript
// config/database.ts
import { Pool, PoolConfig } from "pg";
const poolConfig: PoolConfig = {
host: process.env.DB_HOST,
port: parseInt(process.env.DB_PORT || "5432"),
database: process.env.DB_NAME,
user: process.env.DB_USER,
password: process.env.DB_PASSWORD,
max: 20,
idleTimeoutMillis: 30000,
connectionTimeoutMillis: 2000,
};
export const pool = new Pool(poolConfig);
// Test connection
pool.on("connect", () => {
console.log("Database connected");
});
pool.on("error", (err) => {
console.error("Unexpected database error", err);
process.exit(-1);
});
// Graceful shutdown
export const closeDatabase = async () => {
await pool.end();
console.log("Database connection closed");
};
```
### MongoDB with Mongoose
```typescript
// config/mongoose.ts
import mongoose from "mongoose";
const connectDB = async () => {
try {
await mongoose.connect(process.env.MONGODB_URI!, {
maxPoolSize: 10,
serverSelectionTimeoutMS: 5000,
socketTimeoutMS: 45000,
});
console.log("MongoDB connected");
} catch (error) {
console.error("MongoDB connection error:", error);
process.exit(1);
}
};
mongoose.connection.on("disconnected", () => {
console.log("MongoDB disconnected");
});
mongoose.connection.on("error", (err) => {
console.error("MongoDB error:", err);
});
export { connectDB };
// Model example
import { Schema, model, Document } from "mongoose";
interface IUser extends Document {
name: string;
email: string;
password: string;
createdAt: Date;
updatedAt: Date;
}
const userSchema = new Schema<IUser>(
{
name: { type: String, required: true },
email: { type: String, required: true, unique: true },
password: { type: String, required: true },
},
{
timestamps: true,
},
);
// Indexes
userSchema.index({ email: 1 });
export const User = model<IUser>("User", userSchema);
```
### Transaction Pattern
```typescript
// services/order.service.ts
import { Pool } from "pg";
export class OrderService {
constructor(private db: Pool) {}
async createOrder(userId: string, items: any[]) {
const client = await this.db.connect();
try {
await client.query("BEGIN");
// Create order
const orderResult = await client.query(
"INSERT INTO orders (user_id, total) VALUES ($1, $2) RETURNING id",
[userId, calculateTotal(items)],
);
const orderId = orderResult.rows[0].id;
// Create order items
for (const item of items) {
await client.query(
"INSERT INTO order_items (order_id, product_id, quantity, price) VALUES ($1, $2, $3, $4)",
[orderId, item.productId, item.quantity, item.price],
);
// Update inventory
await client.query(
"UPDATE products SET stock = stock - $1 WHERE id = $2",
[item.quantity, item.productId],
);
}
await client.query("COMMIT");
return orderId;
} catch (error) {
await client.query("ROLLBACK");
throw error;
} finally {
client.release();
}
}
}
```
## Authentication & Authorization
### JWT Authentication
```typescript
// services/auth.service.ts
import jwt from
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