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ARCHITECTURE_DIAGRAM.md

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Microfinance Platform - Architecture Diagram

graph TB
    subgraph "Client Layer"
        W[Web App<br/>React + Vite]
        M[Mobile App<br/>React Native + Expo]
    end
    
    subgraph "API Gateway"
        API[Express Server<br/>Port 5000]
    end
    
    subgraph "Business Logic Layer"
        AUTH[Auth Module]
        CUST[Customer Module]
        LOAN[Loan Module]
        EMI[EMI Module]
        REP[Repayment Module]
        DOC[Document Module]
        RPT[Reports Module]
    end
    
    subgraph "Data Layer"
        DB[(PostgreSQL<br/>Supabase)]
        REDIS[(Redis<br/>Upstash)]
        CLOUD[Cloudinary<br/>File Storage]
    end
    
    subgraph "External Services"
        EMAIL[Email Service<br/>Brevo SMTP]
        CRON[Cron Jobs<br/>Overdue Check]
    end
    
    %% Connections
    W --> API
    M --> API
    
    API --> AUTH
    API --> CUST
    API --> LOAN
    API --> EMI
    API --> REP
    API --> DOC
    API --> RPT
    
    AUTH --> DB
    CUST --> DB
    LOAN --> DB
    EMI --> DB
    REP --> DB
    DOC --> DB
    RPT --> DB
    
    AUTH --> REDIS
    API --> REDIS
    
    DOC --> CLOUD
    
    API --> EMAIL
    CRON --> DB
    CRON --> EMAIL
    
    %% Styling
    classDef client fill:#e1f5fe,stroke:#01579b,stroke-width:2px
    classDef api fill:#f3e5f5,stroke:#4a148c,stroke-width:2px
    classDef business fill:#e8f5e8,stroke:#1b5e20,stroke-width:2px
    classDef data fill:#fff3e0,stroke:#e65100,stroke-width:2px
    classDef external fill:#fce4ec,stroke:#880e4f,stroke-width:2px
    
    class W,M client
    class API api
    class AUTH,CUST,LOAN,EMI,REP,DOC,RPT business
    class DB,REDIS,CLOUD data
    class EMAIL,CRON external
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Component Interactions

1. Authentication Flow

sequenceDiagram
    participant Client
    participant API
    participant Auth
    participant DB
    participant Redis
    
    Client->>API: Login Request
    API->>Auth: Validate Credentials
    Auth->>DB: Find User
    DB-->>Auth: User Data
    Auth->>Auth: Verify Password
    Auth->>Redis: Store Session
    Auth-->>API: JWT Tokens
    API-->>Client: Auth Response
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2. Loan Application Flow

sequenceDiagram
    participant Customer
    participant API
    participant Loan
    participant DB
    participant Admin
    
    Customer->>API: Submit Loan Application
    API->>Loan: Validate Application
    Loan->>DB: Create Loan Record
    Loan->>Loan: Generate EMI Schedule
    DB-->>Loan: Loan Created
    Loan-->>API: Application Submitted
    API-->>Customer: Confirmation
    
    API->>Admin: Notification
    Admin->>API: Review Application
    API->>Loan: Update Status
    Loan->>DB: Save Decision
    DB-->>Loan: Status Updated
    Loan-->>API: Decision Made
    API-->>Customer: Status Update
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3. EMI Payment Flow

sequenceDiagram
    participant Customer
    participant API
    participant EMI
    participant Repayment
    participant DB
    participant Email
    
    Customer->>API: Make Payment
    API->>EMI: Find EMI
    EMI->>DB: Get EMI Details
    DB-->>EMI: EMI Data
    EMI-->>API: EMI Info
    API->>Repayment: Process Payment
    Repayment->>DB: Record Payment
    DB-->>Repayment: Payment Recorded
    Repayment->>Email: Send Receipt
    Repayment-->>API: Payment Success
    API-->>Customer: Confirmation
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Database Schema Overview

Core Tables

  • Users: Authentication and basic user info
  • Customers: Detailed customer information and KYC
  • Loans: Loan applications and details
  • EmiSchedule: EMI payment schedule
  • Repayments: Payment records
  • Documents: Customer documents and KYC files
  • RefreshTokens: JWT refresh tokens

Relationships

User 1:1 Customer
Customer 1:N Loans
Customer 1:N Documents
Loan 1:N EmiSchedule
EmiSchedule 1:1 Repayment
User 1:N RefreshTokens

Technology Stack Details

Backend

  • Runtime: Node.js + TypeScript
  • Framework: Express.js
  • Database: PostgreSQL with Prisma ORM
  • Cache: Redis (Upstash)
  • Authentication: JWT with refresh tokens
  • File Storage: Cloudinary
  • Email: Brevo SMTP
  • Scheduling: Node-cron
  • Logging: Winston

Frontend (Web)

  • Framework: React 18
  • Build Tool: Vite
  • Styling: Tailwind CSS
  • State Management: Zustand
  • Data Fetching: React Query
  • Routing: React Router
  • Forms: React Hook Form + Zod
  • Charts: Recharts

Frontend (Mobile)

  • Framework: React Native
  • Navigation: Expo Router
  • Styling: NativeWind (Tailwind for React Native)
  • State Management: Zustand
  • Data Fetching: React Query
  • Storage: Expo Secure Store

Deployment Architecture

Development Environment

┌─────────────────┐    ┌─────────────���───┐    ┌─────────────────┐
│   Web App       │    │   Mobile App   │    │   API Server    │
│   :5173         │    │   Expo Metro    │    │   :5000         │
└─────────────────┘    └─────────────────┘    └─────────────────┘
         │                       │                       │
         └───────────────────────┼───────────────────────┘
                                 │
                    ┌─────────────────┐
                    │   PostgreSQL    │
                    │   (Supabase)    │
                    └─────────────────┘

Production Environment

┌─────────────────┐    ┌─────────────────┐    ┌─────────────���───┐
│   Web App       │    │   Mobile App    │    │   Load Balancer │
│   (Vercel)      │    │   (App Stores)  │    │                 │
└─────────────────┘    └─────────────────┘    └─────────────────┘
         │                       │                       │
         └───────────────────────┼───────────────────────┘
                                 │
                    ┌─────────────────┐
                    │   API Server    │
                    │   (Cluster)     │
                    └─────────────────┘
                                 │
         ┌───────────────────────┼───────────────────────┐
         │                       │                       │
┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   PostgreSQL    │    │   Redis         │    │   Cloudinary    │
│   (Supabase)    │    │   (Upstash)     │    │   (CDN)         │
└─────────────────┘    └─────────────────┘    └─────────────────┘

Security Architecture

Authentication & Authorization

  • JWT-based authentication
  • Role-based access control (Admin/Customer)
  • Refresh token rotation
  • Password hashing with bcrypt
  • Rate limiting on authentication endpoints

Data Security

  • Input validation with Zod schemas
  • SQL injection prevention via Prisma ORM
  • File upload validation and sanitization
  • Secure file storage with Cloudinary
  • Environment variable protection

API Security

  • CORS configuration
  • Helmet.js for security headers
  • Rate limiting with express-rate-limit
  • Request validation middleware
  • Error handling without sensitive data exposure

Performance Considerations

Database Optimization

  • Prisma query optimization
  • Database indexing on foreign keys
  • Connection pooling
  • Read replicas for scaling

Caching Strategy

  • Redis for session storage
  • API response caching
  • Database query caching
  • Static asset caching

Frontend Optimization

  • Code splitting with React Router
  • Lazy loading components
  • Image optimization
  • Bundle analysis with Vite