Learn with Sandeep

FastAPI project structure that incorporates multiple design patterns including:

• Dependency Injection
• Repository Pattern
• Service Layer
• Strategy Pattern
• Factory Pattern
• Observer Pattern
• Builder Pattern
• Domain-Driven Design (DDD) principles

🧱 Project Structure

fastapi_project/
│
├── app/
│   ├── main.py                  # FastAPI app entry point
│   ├── config.py                # App configuration
│   ├── dependencies/            # DI providers
│   │   ├── db.py
│   │   ├── auth.py
│   │   └── __init__.py
│   │
│   ├── models/                  # Pydantic models
│   │   ├── user.py
│   │   ├── request.py
│   │   └── __init__.py
│   │
│   ├── domain/                  # Domain models (DDD)
│   │   ├── entities/
│   │   │   ├── user_entity.py
│   │   │   └── __init__.py
│   │   └── __init__.py
│   │
│   ├── repositories/            # Repository pattern
│   │   ├── user_repository.py
│   │   └── __init__.py
│   │
│   ├── services/                # Business logic (Service Layer)
│   │   ├── user_service.py
│   │   └── __init__.py
│   │
│   ├── strategies/              # Strategy pattern
│   │   ├── auth/
│   │   │   ├── jwt_strategy.py
│   │   │   ├── oauth_strategy.py
│   │   │   └── __init__.py
│   │   └── __init__.py
│   │
│   ├── factories/               # Factory pattern
│   │   ├── service_factory.py
│   │   └── __init__.py
│   │
│   ├── observers/               # Observer pattern
│   │   ├── event_manager.py
│   │   └── __init__.py
│   │
│   ├── builders/                # Builder pattern
│   │   ├── report_builder.py
│   │   └── __init__.py
│   │
│   ├── middleware/              # Custom middleware
│   │   ├── logging_middleware.py
│   │   └── __init__.py
│   │
│   ├── routes/                  # API routes
│   │   ├── user_routes.py
│   │   └── __init__.py
│   │
│   └── utils/                   # Utility functions
│       ├── helpers.py
│       └── __init__.py
│
├── requirements.txt
└── README.md

🧩 How Patterns Fit Together

Conclusion: In a FastAPI project, you can implement several software design patterns to improve modularity, scalability, and maintainability. Here’s a categorized overview of the most relevant patterns and how they apply to FastAPI

Introduction

As artificial intelligence continues to evolve, it’s essential to distinguish between three foundational yet distinct paradigms: Generative AI, AI Agents, and Agentic AI. While these concepts are closely related, each represents a different level of autonomy, complexity, and capability. This guide breaks down their core differences, practical applications, and how they build upon one another.

1. Generative AI: Creating Content on Demand

What It Is

Generative AI refers to models—like large language models (LLMs) and image generators—that produce original content based on patterns learned from massive datasets. These models are trained on diverse data (text, images, audio, video) and contain billions of parameters.

How It Works

Generative AI is reactive: it responds to user prompts without initiating actions or managing tasks. For example, when prompted to “write a poem about data science,” the model generates a poem but doesn’t decide to write one on its own.

Key Features

• Trained on large, multimodal datasets

• Generates text, images, audio, or video

• Requires prompt engineering to guide output

• Examples: OpenAI’s GPT-4, Meta’s LLaMA 3

• Supported by tools like LangChain, LlamaIndex, and Grok

2. AI Agents: Task-Oriented Intelligence

What They Are

AI agents extend generative AI by adding autonomy and interactivity. They can perform specific tasks by integrating with external tools and APIs, making them more dynamic and useful in real-world applications.

Why They Matter

LLMs alone can’t access real-time or private data. AI agents solve this by making tool calls—requests to external systems—to fetch current or specialized information.

Example Workflow

1. User asks a question.

2. Agent checks if the LLM can answer.

3. If not, it calls an external API (e.g., for today’s news).

4. It processes the response.

5. It delivers a final answer to the user.

Key Features

• Built on LLMs with external tool integration

• Can retrieve real-time or private data

• Perform single, well-defined tasks

• Still reactive, but with enhanced capabilities

• Act autonomously within defined boundaries

3. Agentic AI: Orchestrating Complex Workflows

What It Is

Agentic AI represents the next level—multi-agent systems that collaborate to complete complex, multi-step workflows. Each agent specializes in a subtask, and together they operate like a coordinated team.

Use Case: YouTube to Blog

An agentic AI system might:

1. Extract a transcript from a YouTube video

2. Generate a blog title

3. Write a summary and description

4. Compose a conclusion

Each step is handled by a different agent, and outputs are passed between them to produce a polished blog post.

Key Features

• Multiple agents working in sequence or parallel

• Each agent handles a specific subtask

• Enables end-to-end automation of complex workflows

• Supports human feedback for refinement

• Adds adaptability and robustness through collaboration

4. Comparative Summary

5. Strategic Implications

Generative AI

Ideal for creative content generation, but limited by its reactive nature. Success depends heavily on prompt quality.

AI Agents

Bridge the gap between static models and dynamic applications. Useful in domains like customer service, analytics, and decision support.

Agentic AI

Best suited for automating complex, multi-step processes. Aligns with real-world workflows and supports scalability, adaptability, and human oversight.

Conclusion

Understanding the distinctions between generative AI, AI agents, and agentic AI is essential for anyone working with modern AI systems. From content creation to autonomous task execution and workflow orchestration, these paradigms represent a clear evolution in capability and complexity. By choosing the right approach, organizations can unlock new levels of efficiency, creativity, and intelligence in their AI-driven solutions.