FastAPI Interview Questions and Answers

Answer: All of the above

Async database integration uses async SQLAlchemy, databases library, or motor (MongoDB). Enables non-blocking I/O for better concurrency and performance.

Answer: All of the above

Dependency injection in FastAPI uses Depends() to declare dependencies. It enables code reuse, shared logic, database connections, authentication, etc.

Answer: A modern, fast web framework for building APIs with Python

FastAPI is a modern, fast (high-performance) web framework for building APIs with Python 3.7+ based on standard Python type hints.

Answer: All of the above

Test FastAPI with TestClient: creates client for testing without running server. Use pytest for test framework. Supports async tests with pytest-asyncio.

Answer: Type hints

FastAPI heavily relies on Python type hints for data validation, serialization, and automatic API documentation generation.

Answer: Create a function and use Depends()

Define a dependency as a function, then use it with Depends(): `def get_db(): ...; @app.get("/") def read(db = Depends(get_db)):`. FastAPI calls it automatically.

Answer: pip install fastapi

Install FastAPI using pip: `pip install fastapi`. You also need an ASGI server like uvicorn: `pip install uvicorn[standard]`.

Answer: Both b and c

Sub-dependencies are dependencies that themselves have dependencies. FastAPI resolves the entire dependency tree automatically, creating chains of dependencies.

Answer: All of the above

Override dependencies in tests using app.dependency_overrides dict. Replace real database with test database, mock external APIs, etc.

Answer: app = FastAPI()

Create a FastAPI instance with `app = FastAPI()`. This creates the main application object that you use to define routes and configurations.

Answer: All of the above

Use generator functions with yield for database sessions. Code before yield runs before request, after yield runs after (cleanup). Example: get_db() yields session.

Answer: Both b and c

Integrate GraphQL using Strawberry or Graphene libraries. Add GraphQL endpoint to FastAPI app. Combine REST and GraphQL in same application.

Answer: All of the above

Create custom exception handlers with @app.exception_handler(ExceptionClass). Return custom error responses, log errors, send notifications, etc.

Answer: @app.get()

Use `@app.get("/path")` to define a GET endpoint. FastAPI provides decorators for all HTTP methods: get, post, put, delete, patch, options, head.

Answer: Both b and c

OAuth2PasswordBearer is a security scheme that extracts the bearer token from Authorization header. Used as dependency to protect endpoints.

Answer: All of the above

Implement JWT using python-jose: create tokens with user info and expiry, sign them, return to client. Verify tokens in dependency functions to protect endpoints.

Answer: uvicorn main:app --reload

Run FastAPI with uvicorn: `uvicorn main:app --reload` where main is the filename and app is the FastAPI instance. --reload enables auto-reload during development.

Answer: All of the above

Implement rate limiting using slowapi (Flask-Limiter port) or custom middleware. Limit requests per IP/user per time window. Prevents abuse and DDoS.

Answer: All of the above

Implement pagination with skip/limit query parameters. Return paginated data with total count. Create reusable pagination dependency for consistency.

Answer: Both b and c

APIRouter creates modular, reusable route groups. Define routes in separate files/modules, then include them in main app with app.include_router().

Answer: Auto-generated interactive docs at /docs and /redoc

FastAPI automatically generates interactive API documentation. Access Swagger UI at /docs and ReDoc at /redoc. Based on OpenAPI standard.

Answer: Both b and c

StreamingResponse sends content in chunks without loading entire response in memory. Useful for large files, video streaming, or generated content.

Answer: All of the above

Create router with APIRouter(), define routes on it, then include: `app.include_router(router, prefix="/items", tags=["items"])`.

Answer: Using curly braces in path

Define path parameters using curly braces: `@app.get("/items/{item_id}")`. The parameter is automatically passed to the function and validated.