Flask

Flask offers one of the smoothest getting-started experiences in Python web development. The decorator-based routing (`@app.route()`) is immediately intuitive, and the request/response pattern feels natural. Error messages are generally clear, though tracebacks in development mode can be verbose when dealing with blueprint registration issues.

The documentation is comprehensive with a well-maintained tutorial and patterns section that covers real-world scenarios like database integration and authentication. However, the lack of native type hints in core APIs (Flask 2.x and earlier 3.x versions) means IDE autocompletion is hit-or-miss. You'll find yourself checking docs for `request.args.get()` vs `request.form.get()` more than you'd like. The framework doesn't enforce much structure, which is liberating for small projects but can lead to inconsistent patterns in larger codebases without discipline.

Migration between versions has historically been smooth, with clear deprecation warnings. The extension ecosystem (Flask-SQLAlchemy, Flask-Login) follows similar patterns, making them easy to integrate once you understand Flask's application context and blueprints concept.

Flask's simplicity is both its strength and weakness in production. The framework itself is remarkably lightweight with minimal overhead, but you're responsible for essentially everything operational. The development server is explicitly not production-ready, so you'll immediately need to pair it with Gunicorn or uWSGI. Connection pooling isn't built-in—you manage database connections through extensions like Flask-SQLAlchemy, and misconfiguration leads to connection exhaustion quickly under load.

Error handling requires deliberate setup. The @app.errorhandler decorator works well, but there's no structured logging out of the box. You'll wire up your own logging configuration, ideally early in app initialization. The application context and request context can trip you up—accessing request objects outside the request scope throws runtime errors that aren't always obvious during development. Flask 3.x dropped Python 2 support and changed some import paths, but migrations have been relatively smooth.

Timeout behavior depends entirely on your WSGI server configuration. Flask itself has no timeout defaults, which means you need to configure read/write timeouts at the Gunicorn/uWSGI layer and handle long-running requests carefully. Under load, you'll notice Flask doesn't impose many guardrails—no built-in rate limiting, circuit breakers, or backpressure mechanisms.

Flask delivers an outstanding getting-started experience with minimal boilerplate. The decorator-based routing (`@app.route()`) feels intuitive, and error messages are generally clear when things go wrong. The request/response objects are globally accessible via context locals, which is convenient but can confuse newcomers unfamiliar with the pattern. Documentation is comprehensive with a solid quickstart and extensive patterns section covering real-world scenarios.

The extension ecosystem is mature with well-documented options for JWT, CORS, SQLAlchemy integration, and more. However, this is where DX pain points emerge—many extensions use different configuration patterns, and discovering the "right" extension for a task requires research. IDE autocompletion works reasonably well, but type hints are inconsistent across core APIs and especially sparse in popular extensions.

Migration between versions has been smooth in my experience, with clear upgrade guides. The Blueprint system for modularizing apps is elegant once understood, though the documentation could better explain when and why to use them. Overall, Flask excels at getting out of your way while providing enough structure to build maintainable applications.