BackTrack - Lost & Found Platform

Microservices-based lost and found system with Firebase authentication, real-time chat, and push notifications.

Overview

BackTrack is a platform for posting and finding lost items. Users can create posts for lost/found items, search and match items, chat with other users, and receive notifications.

Architecture

┌─────────────────────────────────────────────────────────────┐
│                          Clients                            │
│         (Mobile Apps, Web Apps, Third-party Apps)          │
└────────────────────────┬────────────────────────────────────┘
                         │
                         │ Firebase ID Token
                         ▼
            ┌────────────────────────┐
            │     API Gateway        │ ← Firebase Auth
            │   (YARP, .NET 8)       │ ← Correlation ID
            └─────────┬──────────────┘ ← Request Routing
                      │
        ┌─────────────┼─────────────┬────────────────┐
        │             │             │                │
        ▼             ▼             ▼                ▼
  ┌─────────┐  ┌──────────┐  ┌──────────┐  ┌──────────────┐
  │  Core   │  │   Chat   │  │ Notify   │  │   Future     │
  │ Service │  │ Service  │  │ Service  │  │  Services    │
  └────┬────┘  └────┬─────┘  └────┬─────┘  └──────────────┘
       │            │             │
       ▼            ▼             ▼
  ┌─────────┐  ┌──────────┐  ┌──────────┐
  │   DB    │  │ MongoDB  │  │   DB     │
  │(SQL/PG) │  │          │  │(SQL/PG)  │
  └─────────┘  └──────────┘  └──────────┘

Services

Service	Technology	Port	Purpose	Status
API Gateway	.NET 8, YARP	5000	Auth, routing, correlation	✅ Complete
Core Service	.NET 8, Clean Architecture	8080	Posts, search, matching	🚧 In Progress
Chat Service	Node.js	3000	Real-time messaging	📝 Planned
Notifications	.NET 8	7000	Push notifications (FCM)	📝 Planned

Each service has its own database and can be deployed independently.

Technology Stack

Layer	Technology
API Gateway	.NET 8, YARP 2.2.0, Firebase Admin SDK
Backend Services	.NET 8 (Clean Architecture, CQRS, MediatR), Node.js 18+
Databases	PostgreSQL, MongoDB
Authentication	Firebase Authentication
Real-time	SignalR / Socket.io
Notifications	Firebase Cloud Messaging (FCM)
Containerization	Docker, Docker Compose

Core Service Architecture

The Core Service follows Clean Architecture with CQRS pattern:

• Contract Layer: Request/Response DTOs with FluentValidation
• Application Layer: Commands, Queries, and MediatR Handlers
• Domain Layer: Entities, Value Objects, Domain Logic
• Infrastructure Layer: Database, Repositories, External Services
• WebApi Layer: Controllers, Middleware, Configuration

Project Structure

service-backtrack/
├── Backtrack.ApiGateway/              # API Gateway service
│   ├── Middleware/                    # Auth & correlation middlewares
│   └── examples/                      # Auth client, token helpers
├── Backtrack.Core/                    # Core service (Clean Architecture)
│   ├── Backtrack.Core.WebApi/         # Controllers, Middleware
│   ├── Backtrack.Core.Application/    # Commands, Queries, Handlers
│   ├── Backtrack.Core.Contract/       # Request/Response DTOs
│   ├── Backtrack.Core.Domain/         # Entities, Value Objects
│   └── Backtrack.Core.Infrastructure/ # Database, Repositories
├── BackTrack.Chat/                    # Chat service (planned)
├── BackTrack.Notifications/           # Notifications service (planned)
├── docker-compose.yml                 # Orchestration
├── .env.example                       # Environment template
└── README.md

Quick Start

Prerequisites

• .NET 8 SDK
• Node.js 18+ (for Chat service)
• Docker & Docker Compose (optional)
• Firebase project

1. Clone and Setup

git clone <repository-url>
cd service-backtrack

# Copy environment template
cp .env.example .env
# Edit .env with your configuration

2. Firebase Setup

1. Create Firebase project at Firebase Console
2. Enable Authentication methods (Email/Password, Google Sign-In)
3. Download service account:
   • Project Settings > Service Accounts > Generate New Private Key
   • Save as firebase-service-account.json in project root (DO NOT commit!)

3. Run with Docker Compose

# Start all services
docker-compose up -d

# View logs
docker-compose logs -f

# Stop all services
docker-compose down

Services will be available at:

• API Gateway: http://localhost:5000
• Core Service: http://localhost:8080

4. Run Locally (Development)

# Terminal 1: API Gateway
cd Backtrack.ApiGateway
export GOOGLE_APPLICATION_CREDENTIALS="../firebase-service-account.json"
dotnet run

# Terminal 2: Core Service
cd Backtrack.Core/Backtrack.Core.WebApi
dotnet run --urls "http://localhost:8080"

Configuration

Environment Variables

Create .env file (see .env.example):

# Firebase
FIREBASE_PROJECT_ID=your-firebase-project-id

# Database connections
CORE_DB_CONNECTION=Host=localhost;Database=backtrack_core;Username=postgres;Password=yourpassword
CHAT_DB_CONNECTION=mongodb://localhost:27017/backtrack_chat
NOTIFY_DB_CONNECTION=Host=localhost;Database=backtrack_notifications;Username=postgres;Password=yourpassword

Service Configuration

Each service has its own appsettings.json:

• API Gateway: Backtrack.ApiGateway/appsettings.json
• Core Service: Backtrack.Core/Backtrack.Core.WebApi/appsettings.json

---

Current Status: API Gateway ✅ | Core Service 🚧 | Chat Service 📝 | Notifications 📝