Understanding The Blockchain Ecosystem & Architecture

Blockchain application Architecture is similar Model View Controller architecture.
Our controllers communicate to blockchain and Distributed Hash Tables rather than we servers and database servers.
We have smart models, thin controllers, and dumb views.
certain elements that need consensus via smart contracts that would usually require a server (like usernames or financial actions)
Smart contracts are in a way models, and we can feed data into them via transactions, but they are not the class like Model in typical MVC architecture.

They can work alongside your existing models, but their utility applies in specific scenarios. These will come up on a case-by-case basis.