Flask is so simple that it's definitely worth picking that up regardless (in any case, I think it's well done and worth having in your arsenal). However, for l

Flask is so simple that it's definitely worth picking that up regardless (in any case, I think it's well done and worth having in your arsenal). However, for large web projects, Django beats it hands down. Doing similar work with Flask would require so much wheel-reinvention that it'd be hard to justify your time or your client's money when it's all built quite well already. Of course it's not perfect, and it's not for everything. But it's a great general-purpose, medium-performance web framework. It becomes a pain on very high-traffic sites (perhaps more so than JVM-based solutions and on par with scaling Ruby frameworks), but if you use it in the right place and/or team up with systems people that know their stuff, it's a powerful tool for quickly building complex websites in a maintainable and intuitive way.