🐾PetConnect Backend

Scalable microservice backend powering intelligent pet adoption, fostering, and shelter management.

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Quick Start

1. Copy .env.example → .env and update configuration values.

2. Install dependencies:

   npm install

3. Start development server (with nodemon):

   npm run dev

4. Start production server:

   npm start

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Scripts

Command	Description
npm run dev	Start dev server with nodemon
npm run lint	Run ESLint for code quality
npm run format	Run Prettier for consistent formatting
npm start	Start production server (node index.js)

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Architecture

• Framework: Node.js + Express
• Database: MongoDB (via Mongoose)
• Architecture Pattern: MVCS (Model–View–Controller–Service)
• Collections: users, pets, organizations, appointments, analytics, etc.
• Deployment: Independent microservice (Docker / Render / Railway / Kubernetes)

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Why MVCS + Caching Instead of MVCSR (with Repositories)

As a team of four developers, our priority is building scalable, performant features quickly — not overengineering abstractions.

Practical Simplicity

The MVCS (Model–View–Controller–Service) pattern provides clear separation of concerns:

• Models define database schemas and validations.
• Controllers handle routing and API flow.
• Services manage all business logic and integrate caching.
• Views define response structures (for API or admin UI).

Adding Repositories (MVCSR) introduces extra abstraction layers — often duplicating logic already handled by Mongoose and slowing development.

Real Performance Gains

Instead of abstraction, we focused on caching, which directly improves user experience:

• 10–100× faster responses for frequently accessed data (e.g., pet listings, user profiles).
• Reduced database load through service-level caching (Redis-ready, easily extensible).
• Enables both speed and scalability with minimal code overhead.

Future-Ready

This architecture is:

• Modular — each service is independently testable.
• Flexible — can evolve to Redis or distributed cache tiers later.
• Maintainable — simple for a small, fast-moving team without losing clarity.

In short: MVCS + Caching gives us clarity, performance, and scalability — without the complexity that repository layers add.

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Tech Stack

Layer	Technology / Library
Runtime	Node.js (v18+)
Framework	Express.js
Database	MongoDB + Mongoose
Authentication	JWT (JSON Web Tokens)
File Uploads	Multer + Cloudinary
Email Service	Nodemailer
Payments	Stripe
Blockchain Integration	Web3.js + Hardhat
PDF Generation	PDFKit, PDF-Lib, @pdf-lib/fontkit
Image Processing	Canvas
Real-Time Communication	Socket.io
HTTP Client	Axios / node-fetch
Environment Management	dotenv
Validation & Security	bcryptjs, cors
Caching	Service-level in-memory (Redis-ready)
Testing	Supertest
Linting & Formatting	ESLint + Prettier

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Environment Variables

Create a .env file in the root directory with:

# Server
PORT=5000
NODE_ENV=development

# Database
MONGO_URI=mongodb+srv://...

# JWT Auth
JWT_SECRET=your_jwt_secret_key

# Cloudinary
CLOUDINARY_CLOUD_NAME=...
CLOUDINARY_API_KEY=...
CLOUDINARY_API_SECRET=...

# Stripe
STRIPE_SECRET_KEY=...

# Email
EMAIL_USER=...
EMAIL_PASS=...

# Blockchain / Web3
WALLET_PRIVATE_KEY=...
INFURA_PROJECT_ID=...

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Folder Structure

│
├── controllers/        # Route controllers (API logic)
├── models/             # Mongoose models and schemas
├── services/           # Business logic + caching layer
├── routes/             # Express routes
├── config/             # DB and environment configuration
├── utils/              # Helpers and shared utilities
├── public/             # Static files (if any)
├── index.js / server.js# Entry point
└── .env.example        # Environment variable template

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MVCS + Caching Flow

flowchart LR
    A[Client Request] --> B[Controller]
    B --> C[Service Layer]
    C -->|Cache Hit| D[Cache]
    C -->|Cache Miss| E[(MongoDB)]
    E --> F[Return Data]
    F --> G[Update Cache]
    G --> H[Send Response to Client]

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Notes for Code Review

• Entry Point: server.js or index.js
• Models: Defined using mongoose.Schema
• Services: Contain core logic and caching mechanisms
• Controllers: Manage request-response flow
• Docs: Add ER diagrams or model documentation here

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License

This project is licensed under the MIT License — free to use, modify, and distribute.

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🧡 PetConnect Backend — built for performance, simplicity, and real-world scalability.