Architecture

Understanding Pestle's technical architecture helps with deployment, integration, and troubleshooting.

System Overview

Pestle is built on a modern, scalable architecture:

┌─────────────────────────────────────────────────────────────┐
│                        Load Balancer                         │
│                    (nginx / cloud LB)                        │
└─────────────────────────┬───────────────────────────────────┘
                          │
          ┌───────────────┴───────────────┐
          │                               │
          ▼                               ▼
┌─────────────────────┐       ┌─────────────────────┐
│     Frontend        │       │      Backend        │
│    (SvelteKit)      │       │     (Django)        │
│    Port: 3000       │       │    Port: 8000       │
└─────────────────────┘       └──────────┬──────────┘
                                         │
                    ┌────────────────────┼────────────────────┐
                    │                    │                    │
                    ▼                    ▼                    ▼
          ┌─────────────────┐  ┌─────────────────┐  ┌─────────────────┐
          │   PostgreSQL    │  │     Redis       │  │  File Storage   │
          │   (Database)    │  │    (Cache)      │  │   (S3/Local)    │
          └─────────────────┘  └─────────────────┘  └─────────────────┘

Components

Frontend (SvelteKit)

• Framework: SvelteKit with TypeScript
• Styling: Tailwind CSS + Skeleton UI
• State Management: Svelte stores
• i18n: Paraglide for translations
• Build: Vite

Backend (Django)

• Framework: Django 4.x + Django REST Framework
• Database ORM: Django ORM
• Authentication: Django AllAuth + JWT
• Task Queue: Celery (optional)
• API Docs: OpenAPI/Swagger

Database (PostgreSQL)

• Version: PostgreSQL 14+
• Features used: JSONB fields, full-text search, UUID primary keys
• Migrations: Django migrations

Cache (Redis)

• Session storage
• API response caching
• Celery broker (if using async tasks)

Data Model

Core Entities

Folder (organizational container)
├── Risk
│   ├── RiskScenario
│   └── RiskTreatment
├── AppliedControl
│   └── Evidence
├── ComplianceAssessment
│   └── AssessmentResult
├── TaskTemplate
│   └── TaskNode (occurrences)
└── Policy
    └── PolicyDocument

Key Relationships

• Folders contain all other objects and define permissions scope
• Risks link to AppliedControls for mitigation tracking
• AppliedControls map to Framework Requirements
• Tasks can be assigned to users with due dates

Security Architecture

Authentication Flow

User → Login → Identity Provider (or local) → JWT Token → API Access

Authorization (RBAC)

Request → Middleware → Check User Roles → Check Folder Permissions → Allow/Deny

Data Protection

• Encryption in transit: TLS 1.3
• Encryption at rest: AES-256 (cloud) or filesystem encryption (self-hosted)
• Secrets management: Environment variables or vault integration

Scalability

Horizontal Scaling

• Frontend: Stateless, can run multiple instances behind load balancer
• Backend: Stateless API, scales horizontally
• Database: Read replicas for reporting workloads

Performance Optimizations

• Database query optimization with select_related/prefetch_related
• Redis caching for frequently accessed data
• Pagination for large datasets
• Async task processing for heavy operations

Integration Points

Inbound

• REST API: Full CRUD operations
• SSO/SAML: Identity provider integration
• File Import: CSV, Excel, JSON

Outbound

• Webhooks: Event notifications
• Email: SMTP for notifications
• Export: Reports, data exports

Monitoring & Observability

• Logging: Structured JSON logs
• Metrics: Prometheus-compatible endpoints
• Health checks: /health and /ready endpoints
• Tracing: OpenTelemetry support

Development Setup

# Clone and setup
git clone https://github.com/your-org/pestle.git
cd pestle

# Backend
cd backend
python -m venv venv
source venv/bin/activate
pip install -r requirements.txt
python manage.py migrate
python manage.py runserver

# Frontend (new terminal)
cd frontend
npm install
npm run dev