CHECK constraint introduced, when make it really useful?

I could find the release note when you introduced the CHECK constraint. In an extremely limited form. What I need is that I for example don't have overlapping timespans in a database in a multi-threading environment. A CHECK constraint which goes over all already existing rows is the perfect solution, it works on other databases, but not on MariaDB. A simple CHECK if "a > b" like in your example could be done easily in program code, ignoring race conditions, no real advantage there for the CHECK constraint.

So: When will you introduce a useful CHECK constraint into MariaDB? Or did I just overlook it in the release notes?