Can you explain what FastAPI is and what it is used for in web application development?

FastAPI is a modern, fast (high-performance) web framework for building APIs with Python. Its main features:

• Uses standard Python type hints for automatic data validation and documentation generation.
• Very high performance thanks to ASGI and Starlette.
• Simplicity and ease of development due to a declarative style and automatic OpenAPI and Swagger UI generation.

FastAPI is often used for developing RESTful APIs and microservices where development speed and high performance are important.

Example of a simple FastAPI application:

from fastapi import FastAPI

app = FastAPI()

@app.get("/hello")
async def read_hello():
    return {"message": "Hello, FastAPI!"}

Such an application can be quickly deployed and integrated with a frontend or other services.