Check out our "temporary assign" documentation – you only hold on to the state you need. That said, you are right that a LV application will necessarily use more memory than a stateless JSON API, but there is more nuance to the story. A LiveView application will use less resources under application operation than a single page app, for example:

- because LiveViews are stateful, we don't have to refetch/reload the state we need on every "request". Things like current_user, current organization, preferences, etc. So what we lose in memory load, we gain in reduced DB and system load, caching strategies, etc

- because LiveViews are stateful with change-tracking, we actually can send less data than the best hand-written SPA/JSON application you could write. So what we lose in memory load, we gain in reduced latency and overall data on the wire.

Direct link to data-on-the-wire example from my keynote for those curious: https://youtu.be/txk4WAlabvI?t=873