FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints. It is designed to be easy to use, fast to code, and suitable for production environments. Here are some advantages and disadvantages of using FastAPI:

Advantages:

1. Fast performance: FastAPI is built on top of Starlette and Pydantic, which makes it one of the fastest Python web frameworks available. It offers high performance on par with Node.js and Go web frameworks.

2. Easy to learn and use: FastAPI provides a simple and intuitive way to define routes, request/response models, and handle HTTP requests. It uses Python type hints to define and validate request and response data, making the code more readable and self-documenting.

3. Automatic API documentation: FastAPI automatically generates interactive API documentation using Swagger UI and ReDoc. This allows developers and API consumers to easily explore and test the API endpoints without the need for external documentation tools.

4. Validation and serialization: With the help of Pydantic, FastAPI provides automatic request validation and serialization. It ensures that the incoming data matches the defined schema and validates it before processing, reducing the chances of errors and improving security.

5. Asynchronous support: FastAPI supports asynchronous programming using the async and await syntax. This allows for efficient handling of concurrent requests and enables better utilization of system resources.

6. Extensibility: FastAPI is highly extensible and integrates well with other libraries and frameworks. It supports dependency injection, middleware, and plug-ins, allowing developers to customize and extend the functionality as needed.

Disadvantages:

1. Limited ecosystem: Compared to more established web frameworks like Django or Flask, FastAPI has a relatively smaller ecosystem. This means that there may be fewer third-party packages, extensions, and community resources available for FastAPI.

2. Lack of built-in features: FastAPI focuses primarily on building APIs and does not provide many built-in features for full-stack web development. If you need features like database ORM, authentication, or template rendering, you'll need to integrate additional libraries or frameworks.

3. Learning curve for advanced features: While FastAPI is easy to get started with, some of its advanced features, such as dependency injection and asynchronous programming, may have a steeper learning curve for developers who are new to these concepts.

4. Limited support for older Python versions: FastAPI requires Python 3.6 or above due to its reliance on type hints and modern Python features. If you are working on a project that requires support for older Python versions, you may need to consider alternative frameworks.

5. Relatively new framework: FastAPI is a relatively new framework compared to other establishe