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. Use when this capability is needed.
metadata	{"author":"AI-Foundry-Core"}

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",
        : [, ],
        : {
          : { : , :  },
          : { : , :  },
        },
      },
    },
  },
   (request, reply) => {
     { name, email } = request.;
     { : , name };
  },
);

 fastify.({ : , :  });

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: , : , : ) {
     {
       { id } = req.;
       user =  ..(id);
      res.(user);
    }  (error) {
      (error);
    }
  }

   () {
     {
       { id } = req.;
       :  = req.;
       user =  ..(id, updates);
      res.(user);
    }  (error) {
      (error);
    }
  }

   () {
     {
       { id } = req.;
       ..(id);
      res.().();
    }  (error) {
      (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, );

    
     user =  ..({
      ...userData,
      : hashedPassword,
    });

    
     { password, ...userWithoutPassword } = user;
     userWithoutPassword  ;
  }

   (: ): <> {
     user =  ..(id);
     (!user) {
        ();
    }
     { password, ...userWithoutPassword } = user;
     userWithoutPassword  ;
  }

   (: , : ): <> {
     user =  ..(id, updates);
     (!user) {
        ();
    }
     { password, ...userWithoutPassword } = user;
     userWithoutPassword  ;
  }

   (: ): <> {
     deleted =  ..(id);
     (!deleted) {
        ();
    }
  }
}

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 } =  ..(query, [id]);
     rows[] || ;
  }

   (: ): < | > {
     query = ;
     { rows } =  ..(query, [email]);
     rows[] || ;
  }

   (: , : ): < | > {
     fields = .(updates);
     values = .(updates);

     setClause = fields
      .( )
      .();

     query = ;

     { rows } =  ..(query, [id, ...values]);
     rows[] || ;
  }

   (: ): <> {
     query = ;
     { rowCount } =  ..(query, [id]);
     rowCount > ;
  }
}

Pattern 2: Dependency Injection

DI Container:

// 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: , :  T):  {
     : T;
    ..(key,  {
       (!instance) {
        instance = ();
      }
       instance;
    });
  }
}

  container =  ();


container.(
  ,
  
     ({
      : process..,
      : (process.. || ),
      : process..,
      : process..,
      : process..,
      : ,
      : ,
      : ,
    }),
);

container.(
  ,
    (container.()),
);

container.(
  ,
    (container.()),
);

container.(
  ,
    (container.()),
);

container.(
  ,
    (container.()),
);

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.(token, process..!)  ;

    req. = payload;
    ();
  }  (error) {
    ( ());
  }
};

   = () => {
    (: , : , : ) => {
     (!req.) {
       ( ());
    }

    
     hasRole = roles.( req.?.?.(role));

     (!hasRole) {
       ( ());
    }

    ();
  };
};

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(),
          : err.,
        }));
        ( (, errors));
      }  {
        (error);
      }
    }
  };
};


 { z }  ;

 createUserSchema = z.({
  : z.({
    : z.().(),
    : z.().(),
    : z.().(),
  }),
});

router.(, (createUserSchema), userController.);

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({
    : redis,
    : ,
  }),
  :  *  * ,
  : , 
  : ,
});

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`,
      : req.[],
      : req.,
    });
  });

  ();
};

 { 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, );
  }
}

     {
  () {
    (message, );
  }
}

     {
  () {
    (message, );
  }
}

     {
  () {
    (message, );
  }
}

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
   message =
    process.. === 
      ? 
      : err.;

  res.().({
    : ,
    message,
  });
};


   = () => {
    {
    .((req, res, next)).(next);
  };
};

Database Patterns

PostgreSQL with Connection Pool

// 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
   =  () => {
   pool.();
  .();
};

MongoDB with Mongoose

// 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";

    {
  : ;
  : ;
  : ;
  : ;
  : ;
}

 userSchema =  <>(
  {
    : { : , :  },
    : { : , : , :  },
    : { : , :  },
  },
  {
    : ,
  },
);


userSchema.({ :  });

   = model<>(, userSchema);

Transaction Pattern

// 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],
        );

        
         client.(
          ,
          [item., item.],
        );
      }

       client.();
       orderId;
    }  (error) {
       client.();
       error;
    }  {
      client.();
    }
  }
}

Authentication & Authorization

JWT Authentication

// services/auth.service.ts
import jwt from "jsonwebtoken";
import bcrypt from "bcrypt";
import { UserRepository } from "../repositories/user.repository";
import { UnauthorizedError } from "../utils/errors";

export class AuthService {
  constructor(private userRepository: UserRepository) {}

  async login(email: string, password: string) {
    const user = await this.userRepository.findByEmail(email);

    if (!user) {
      throw new UnauthorizedError("Invalid credentials");
    }

    const isValid = await bcrypt.compare(password, user.password);

    if (!isValid) {
      throw new UnauthorizedError("Invalid credentials");
    }

    const token = this.({
      : user.,
      : user.,
    });

     refreshToken = .({
      : user.,
    });

     {
      token,
      refreshToken,
      : {
        : user.,
        : user.,
        : user.,
      },
    };
  }

   () {
     {
       payload = jwt.(
        refreshToken,
        process..!,
      )  { :  };

       user =  ..(payload.);

       (!user) {
          ();
      }

       token = .({
        : user.,
        : user.,
      });

       { token };
    }  (error) {
        ();
    }
  }

   (: ):  {
     jwt.(payload, process..!, {
      : ,
    });
  }

   (: ):  {
     jwt.(payload, process..!, {
      : ,
    });
  }
}

Caching Strategies

// utils/cache.ts
import Redis from "ioredis";

const redis = new Redis({
  host: process.env.REDIS_HOST,
  port: parseInt(process.env.REDIS_PORT || "6379"),
  retryStrategy: (times) => {
    const delay = Math.min(times * 50, 2000);
    return delay;
  },
});

export class CacheService {
  async get<T>(key: string): Promise<T | null> {
    const data = await redis.get(key);
    return data ? JSON.parse(data) : null;
  }

  async set(key: string, value: any, ttl?: number): Promise<void> {
    const serialized = JSON.stringify(value);
     (ttl) {
       redis.(key, ttl, serialized);
    }  {
       redis.(key, serialized);
    }
  }

   (: ): <> {
     redis.(key);
  }

   (: ): <> {
     keys =  redis.(pattern);
     (keys. > ) {
       redis.(...keys);
    }
  }
}


  () {
    () {
     originalMethod = descriptor.;

    descriptor. =   () {
       cache =  ();
       cacheKey = ;

       cached =  cache.(cacheKey);
       (cached) {
         cached;
      }

       result =  originalMethod.(, args);
       cache.(cacheKey, result, ttl);

       result;
    };

     descriptor;
  };
}

API Response Format

// utils/response.ts
import { Response } from "express";

export class ApiResponse {
  static success<T>(
    res: Response,
    data: T,
    message?: string,
    statusCode = 200,
  ) {
    return res.status(statusCode).json({
      status: "success",
      message,
      data,
    });
  }

  static error(res: Response, message: string, statusCode = 500, errors?: any) {
    return res.status(statusCode).json({
      status: "error",
      message,
      ...(errors && { errors }),
    });
  }

  static paginated<T>(
    res: Response,
    data: T[],
    page: number,
    limit: number,
    total: number,
  ) {
    return res.json({
      status: "success",
      data,
      pagination: {
        page,
        limit,
        total,
        : .(total / limit),
      },
    });
  }
}

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.

Resources

• Node.js Best Practices: https://github.com/goldbergyoni/nodebestpractices
• Express.js Guide: https://expressjs.com/en/guide/
• Fastify Documentation: https://www.fastify.io/docs/
• TypeScript Node Starter: https://github.com/microsoft/TypeScript-Node-Starter

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Source: AI-Foundry-Core/ril-agents — distributed by TomeVault.