... they don't. Most games contain gigabytes of static data, a whole bunch of ephemeral data that is recreated and discarded every frame, and the actual mutable

... they don't. Most games contain gigabytes of static data, a whole bunch of ephemeral data that is recreated and discarded every frame, and the actual mutable state that persists across frames is rarely more than a few hundred kB, unless you are making a huge open-world game (in which case it's still probably less than tens of megabytes.) This persistent data is what you use transactions on, and there are past experiments of doing things like fully double-buffering this state (Each frame, recreate the full state into a different buffer, with the code doing so only touching the previous frame, never reading from the current one. Great for multi-threading!)