This post addresses some bad habits. I’ve seen a common thread in old apps, both my own and others’, where data which belongs in one model is duplicated and stored in another model, either for performance or convenience reasons. Knowing a few fundamentals of development, architecture and knowledge of the right tools for each job solves that.

http://blog.nrowegt.com/development-tools-srp-demeter-architecture-and-putting-code-and-functionality-where-it-belongs/