Whether application state is short-lived (e.g., request/response CRUD) or long-lived (e.g., an in-memory interactive UI) is orthogonal to MVC. MVC is a structural separation of responsibilities between model, view, and control logic. The duration of state affects implementation strategy, not the applicability of the pattern itself.

MVC is a structural separation of responsibilities between model, view, and control logic.

Yes, but the “MVC” pattern used by various back-end web frameworks that borrowed the term a while back actually has very little to do with the original MVC of the Reenskaug era.

The original concept of MVC is based on a triangle of three modules with quite specific responsibilities and relationships. The closest equivalent on the back-end of a web application might be having a data model persisted via a database or similar, and then a web server providing a set of HTTP GET endpoints allowing queries of that model state (perhaps including some sort of WebSocket or Server-Sent Event provision to observe any changes) and a separate set of HTTP POST/PUT/PATCH endpoints allowing updates of the model state. Then on the back end, your “view” code handles any query requests, including monitoring the model state for changes and notifying any observers via WS/SSE, while your “controller” code handles any mutation requests. And then on the front end, you render your page content based on the back-end view endpoints, subscribe for notifications of changes that cause you to update your rendering, and any user interactions get sent to the back-end controller endpoints.

In practice, I don’t recall ever seeing an “MVC” back-end framework used anything like that. Instead, they typically have a “controller” in front of the “model” and have it manage all incoming HTTP requests, with “view” referring to the front-end code. This is fundamentally a tiered, linear relationship and it allocates responsibilities quite differently to the original, triangular MVC.