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FastAPI Backend API

This project implements a Backend API using FastAPI, following a modular architecture and leveraging dependency injection as the primary mechanism for authentication, authorization, and cross-cutting concerns.

🧭 Responsibilities of This API

  • Expose RESTful HTTP endpoints
  • Handle request validation and response serialization
  • Enforce authentication and authorization via dependency injection
  • Orchestrate domain services and business workflows
  • Interact with persistence layers through repositories
  • Provide structured logging and observability

🚫 Non-Responsibilities

  • UI rendering
  • Client-side state management
  • Certificate or TLS management
  • Infrastructure provisioning
  • Hardcoded secrets or credentials

The API must remain stateless and focused on application-level concerns.

🔐 Security Considerations

  • Authentication is implemented using FastAPI dependency injection
  • Authorization rules are enforced at the router or endpoint level
  • Security dependencies are reusable and composable
  • Secrets and credentials are injected via environment variables
  • No secrets are stored in source code or configuration files

Typical authentication mechanisms include: - JWT Bearer tokens - OAuth2 flows - External identity providers

🌱 Dependency Injection Strategy

FastAPI dependencies are used to:

  • Resolve the authenticated user
  • Validate access tokens
  • Enforce authorization rules
  • Inject repositories and services
  • Centralize cross-cutting concerns (logging, tracing)

This ensures: - Loose coupling - High testability - Clear separation of concerns

(FastAPI + Dependency Injection)

This structure promotes clean architecture, maintainability, and scalability, aligning with FastAPI best practices.

app/
│
├─ dependencies/                       # FastAPI dependency providers
│  ├─ auth.py                          # Authentication dependencies
│  ├─ permissions.py                  # Authorization rules
│  └─ database.py                     # DB session dependencies
│
├─ internal/                           # Internal application configuration
│  ├─ config.py                       # App settings and environment config
│  └─ README.md                       # Internal architecture notes
│
├─ migrations/                         # Database migrations
│
├─ models/                             # Domain and ORM models
│
├─ repositories/                      # Data access layer
│
├─ routers/                           # API route definitions
│  ├─ auth.py                         # Auth-related endpoints
│  ├─ users.py                        # User endpoints
│  └─ health.py                       # Health checks
│
├─ schemes/                           # Request and response schemas (Pydantic)
│
├─ services/                          # Business logic and use cases
│
├─ utils/                             # Cross-cutting utilities
│  ├─ constants/
│  │  ├─ app.py                       # Application-level constants
│  │  ├─ environment.py               # Environment names and keys
│  │  └─ messages.py                  # Standard messages and errors
│  │
│  ├─ handlers/                       # Exception and error handlers
│  └─ helpers/
│     └─ functions.py                 # Shared helper functions
│
├─ __init__.py
│
├─ main.py                            # FastAPI application entry point
│
├─ logs/                              # Application logs (runtime-generated)
│
├─ .dockerignore
├─ .env                               # Local environment variables (not committed)
├─ .env.sample                        # Environment variable template
│
├─ Dockerfile_develop                 # Development container image
├─ Dockerfile_production              # Production container image
│
├─ entrypoint_develop.sh              # Dev container startup script
├─ entrypoint_production.sh           # Prod container startup script
│
├─ requirements_base.txt              # Base dependencies
├─ requirements_develop.txt           # Development dependencies
├─ requirements_production.txt        # Production dependencies
│
├─ sshd_config                        # SSH configuration (if required)
└─ README.md                          # API overview and usage