Flask remains one of the most popular Python frameworks for building REST APIs. Its simplicity and flexibility make it an excellent choice for everything from small microservices to large-scale applications. This guide walks through building a production-ready REST API with Flask, covering project structure, authentication, validation, error handling, and testing. Project Setup Directory Structure flask_api/ ├── app/ │ ├── __init__.py │ ├── config.py │ ├── models/ │ │ ├── __init__.py │ │ └── user.py │ ├── routes/ │ │ ├── __init__.py │ │ └── users.py │ ├── services/ │ │ ├── __init__.py │ │ └── user_service.py │ ├── middleware/ │ │ ├── __init__.py │ │ └── auth.py │ └── schemas/ │ ├── __init__.py │ └── user_schema.py ├── tests/ │ ├── __init__.py │ ├── conftest.py │ └── test_users.py ├── migrations/ ├── requirements.txt ├── .flaskenv └── run.py Enter fullscreen mode Exit fullscreen mode Dependencies # requirements.txt Flask==3.1.0 Flask-SQLAlchemy==3.1.1 Flask-Marshmallow==0.15.0 marshmallow==3.23.0…