I have a Rails app in which moderators can manage `meetings` and normal `users` can attend those meetings.

At some point, the admins should be able to "semi-freeze" the app. This is basically setting a period of time (let's call it a "Frozen Period") during which a few things happen:

* as the meetings created before the frozen period starts will be included in a calculation soon, they cannot be `edit`ed during the frozen period.
* moderators can continue to `create` new meetings and `edit` those meetings, as those new meetings won't affect the calculation.
* warnings appear around the site explaining these issues.

In principle I could create a `FrozenPeriod` model, but I don't actually need to store several frozen periods at a time, as they are discarded once they are over.

Therefore, I'm looking for a "global state" type approach. This should still be stored in the database, but maybe without an associated model.

Does this make sense? Do best practices include a way of having a "singleton model" stored in the database, for example?