For quite some time, client-server architecture was one of the most widespread patterns in large-scale software development. Even systems that run purely on one computer are often designed this way. This allows us to clearly separate concerns: the server takes care of heavy business logic, persistent storage, accessing data from third-party services, and so on, and the client is responsible solely for presentation to end users.
This architecture also allows us to have multiple clients connected to one backend: mobile apps, IoT devices, third-party REST API consumers (for example, external developers), and the web, for example.
In the early days of web development, it was not that way though. ...
