---
title: "System Components"
description: "Overview of TraceRTM system components and their interactions"
keywords: [architecture, components, system design]
---

# System Components

Overview of TraceRTM system components and how they interact.

## Component Architecture

```
┌─────────────────────────────────────────┐
│           Client Layer                  │
│  ┌──────┐  ┌──────┐  ┌──────┐         │
│  │ CLI  │  │ TUI  │  │ Web  │         │
│  └──┬───┘  └──┬───┘  └──┬───┘         │
└─────┼─────────┼──────────┼─────────────┘
      │         │          │
      └─────────┴──────────┘
              │
      ┌───────▼────────┐
      │   API Layer    │
      │   (FastAPI)    │
      └───────┬────────┘
              │
      ┌───────▼────────┐
      │ Service Layer  │
      │ (Business Logic)│
      └───────┬────────┘
              │
      ┌───────▼────────┐
      │Repository Layer│
      │  (Data Access) │
      └───────┬────────┘
              │
      ┌───────▼────────┐
      │   Database     │
      │  (PostgreSQL)  │
      └────────────────┘
```

## Core Components

### API Layer

**Location**: `src/tracertm/api/`

**Responsibilities**:
- HTTP request handling
- Request validation
- Response formatting
- Authentication/Authorization

**Key Files**:
- `main.py`: FastAPI app and routes
- `auth.py`: Authentication logic
- `middleware.py`: Request middleware

### Service Layer

**Location**: `src/tracertm/services/`

**Responsibilities**:
- Business logic
- Validation rules
- Orchestration
- Event publishing

**Key Services**:
- `item_service.py`: Item management
- `link_service.py`: Link management
- `project_service.py`: Project management
- `export_service.py`: Data export

### Repository Layer

**Location**: `src/tracertm/repositories/`

**Responsibilities**:
- Data access abstraction
- Query building
- Transaction management

**Key Repositories**:
- `item_repository.py`: Item data access
- `link_repository.py`: Link data access
- `project_repository.py`: Project data access

### Models

**Location**: `src/tracertm/models/`

**Types**:
- **ORM Models**: SQLAlchemy models
- **Schemas**: Pydantic models
- **DTOs**: Data transfer objects

## Supporting Components

### Authentication

**Location**: `src/tracertm/auth/`

**Features**:
- JWT token generation/validation
- API key validation
- OAuth 2.0 support
- Role-based access control

### Events

**Location**: `src/tracertm/events/`

**Features**:
- Event publishing
- Event subscriptions
- Event handlers
- Webhook integration

### Caching

**Location**: `src/tracertm/cache/`

**Features**:
- Redis integration
- Cache invalidation
- Cache strategies

### Storage

**Location**: `src/tracertm/storage/`

**Backends**:
- Local file system
- S3-compatible storage
- Azure Blob Storage

## Component Interactions

### Create Item Flow

```
API Handler
    ↓ calls
Item Service
    ↓ calls
Item Repository
    ↓ queries
Database
    ↓ returns
Item Repository
    ↓ returns
Item Service
    ↓ publishes
Event Bus
    ↓ returns
API Handler
    ↓ returns
Client
```

### Query Flow

```
API Handler
    ↓ calls
Item Service
    ↓ checks
Cache
    ↓ if miss, calls
Item Repository
    ↓ queries
Database
    ↓ stores in
Cache
    ↓ returns
Item Service
    ↓ returns
API Handler
```

## Data Flow

### Request → Response

1. **Client** sends HTTP request
2. **API Layer** validates and routes
3. **Service Layer** applies business logic
4. **Repository Layer** queries database
5. **Database** returns data
6. **Response** flows back through layers

### Event Flow

1. **Service** publishes event
2. **Event Bus** routes to handlers
3. **Handlers** process event
4. **Webhooks** triggered (if configured)

## Component Dependencies

```
API Layer
  depends on → Service Layer
    depends on → Repository Layer
      depends on → Database

Service Layer
  depends on → Event Bus
  depends on → Cache
  depends on → Storage
```

## Related Documentation

- [Request Flow](./02a-request-flow) - Request processing
- [Internals](../developer/internals) - Implementation details
