💸 PayTM-like App: Full-Stack Payments Monorepo

A high-performance, distributed payments platform built with Next.js, Node.js, and PostgreSQL. This project features a decoupled architecture, secure P2P transfers, and an automated bank-webhook processing system.

🚀 Technical Highlights

• Monorepo Architecture: Managed via Turborepo and npm workspaces to optimize build pipelines and enable seamless code sharing across frontend and backend services.
• Decoupled Microservices: Independent deployment of the User-App (Next.js) and Bank-Webhook (Express) for optimized scaling on Render.
• Atomic Transactions: Leverages Prisma Transactions to ensure ACID compliance during wallet balance updates and P2P transfers.
• Security Migration: Successfully transitioned from plaintext storage to Bcrypt hashing, implementing a hybrid "auto-upgrade" logic to secure legacy user data.
• CI/CD & DevOps: Automated deployment pipelines using GitHub Actions and Docker to ensure environment parity and streamlined service updates.

🛠️ Tech Stack

• Frontend: Next.js 14 (App Router), Tailwind CSS, NextAuth.js
• Backend: Node.js, Express.js, TypeScript
• Database: PostgreSQL, Prisma ORM, Neon DB
• Infrastructure: Docker, Render, GitHub Actions, Turborepo

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🏗️ System Design

The application is split into two primary services that share a common database schema and shared TypeScript types:

1. User-App: Handles the UI, user authentication, dashboard visualization, and P2P transfer requests.
2. Bank-Webhook: A "headless" service that listens for external bank notifications to fulfill "Add Money" requests asynchronously.

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🏗️ System Architecture

%%{init: {'theme': 'base', 'themeVariables': { 'primaryColor': '#3b82f6', 'edgeLabelBackground':'#ffffff', 'tertiaryColor': '#f3f4f6'}}}%%
graph TD
    subgraph External ["External Actors"]
        User([👤 User Browser])
        BankApi[🏦 External Bank API]
    end

    subgraph RenderDeployment ["Render Deployment (Monorepo)"]
        style RenderDeployment fill:#f8fafc,stroke:#cbd5e1,stroke-width:2px,stroke-dasharray: 5 5

        subgraph Services ["Microservices"]
            UserApp["🖥️ User App (Next.js)
            (Auth, Dashboard, P2P)"]
            WebhookApp["⚙️ Bank Webhook (Express)
            (Async Balance Updates)"]
        end

        subgraph SharedLibs ["Shared Packages"]
            PrismaClient["📦 @repo/db
            (Prisma Client & Schema)"]
        end
    end

    subgraph DataLayer ["Data Layer"]
        Postgres[(🗄️ PostgreSQL DB
        Neon DB)]
    end

    %% Connections
    User ==>|HTTPS / NextAuth| UserApp
    BankApi ==>|POST Webhook| WebhookApp

    UserApp -.->|Imports| PrismaClient
    WebhookApp -.->|Imports| PrismaClient

    PrismaClient ==>|"TCP Connection
    (Transactions/Queries)"| Postgres

    %% Styling classes
    classDef external fill:#fff1f2,stroke:#e11d48,stroke-width:2px;
    classDef service fill:#dbeafe,stroke:#2563eb,stroke-width:2px;
    classDef shared fill:#f3f4f6,stroke:#64748b,stroke-width:1px,stroke-dasharray: 5 5;
    classDef database fill:#fef3c7,stroke:#d97706,stroke-width:2px;

    class User,BankApi external;
    class UserApp,WebhookApp service;
    class PrismaClient shared;
    class Postgres database;

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🚦 Getting Started

Prerequisites

• Node.js (v18+)
• Docker (Optional)
• PostgreSQL instance (or Neon DB account)

Installation

1. Clone the repository:

   git clone https://github.com/rah7202/paytm.git
   cd paytm

2. Install dependencies:

   npm install

3. Setup Environment Variables: Create a .env file in the root and add your DATABASE_URL and NEXTAUTH_SECRET.

4. Database Migration & Seeding:

   npx prisma migrate dev
   npx prisma db seed

5. Run the application:

   npm run dev

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🐳 Docker Deployment

To run the entire ecosystem (Frontend, Backend, and DB) locally using Docker:

docker-compose up --build