nodejs-backend-patterns

name	nodejs-backend-patterns
description	Build production-ready Node.js backend services with Express/Fastify, implementing middleware patterns, error handling, authentication, database integration, and API design best practices. Use when creating Node.js servers, REST APIs, GraphQL backends, or microservices architectures.

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:

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:

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/
├── controllers/     # Handle HTTP requests/responses
├── services/        # Business logic
├── repositories/    # Data access layer
├── models/          # Data models
├── middleware/      # Express/Fastify middleware
├── routes/          # Route definitions
├── utils/           # Helper functions
├── config/          # Configuration
└── types/           # TypeScript types

Controller Layer:

// 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:

// 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:

// 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

Use a DI container to wire up repositories, services, and controllers. For a full container implementation, see references/advanced-patterns.md.

Middleware Patterns

Authentication Middleware

// 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

// 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

// 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

// 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

// 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

// 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

Node.js supports both SQL and NoSQL databases. Use connection pooling for all production databases.

Key patterns covered in references/advanced-patterns.md:

• PostgreSQL with connection pool — pg Pool configuration and graceful shutdown
• MongoDB with Mongoose — connection management and schema definition
• Transaction pattern — BEGIN/COMMIT/ROLLBACK with pg client

Authentication & Authorization

JWT-based auth with access tokens (short-lived, 15m) and refresh tokens (7d). Full AuthService implementation with bcrypt password comparison in references/advanced-patterns.md.

Caching Strategies

Redis-backed CacheService with get/set/delete/invalidatePattern, plus a @Cacheable decorator for method-level caching. See references/advanced-patterns.md.

API Response Format

Standardized ApiResponse helper with success, error, and paginated static methods. See references/advanced-patterns.md.

Best Practices

1. Use TypeScript: Type safety prevents runtime errors
2. Implement proper error handling: Use custom error classes
3. Validate input: Use libraries like Zod or Joi
4. Use environment variables: Never hardcode secrets
5. Implement logging: Use structured logging (Pino, Winston)
6. Add rate limiting: Prevent abuse
7. Use HTTPS: Always in production
8. Implement CORS properly: Don't use * in production
9. Use dependency injection: Easier testing and maintenance
10. Write tests: Unit, integration, and E2E tests
11. Handle graceful shutdown: Clean up resources
12. Use connection pooling: For databases
13. Implement health checks: For monitoring
14. Use compression: Reduce response size
15. Monitor performance: Use APM tools

Testing Patterns

See javascript-testing-patterns skill for comprehensive testing guidance.

Compact Rules

• Validate all external input at system boundaries; trust internal code
• Use async/await; handle errors with try/catch or centralized error middleware
• Never store secrets in code — environment variables only
• Structure: routes → controllers → services → repositories
• Use connection pooling; never open a new connection per request
• JSON file-store: use ensureDefaultFiles + readFile→mutate→writeFile (single-server, no locking)
• JWT with jose: SignJWT + jwtVerify, TextEncoder-encoded secret, parse Authorization: Bearer header