I hope you remember to add monitoring for your cache expiry cron job so you can be notified if it ever fails to run due to a code change or configuration change. For example, database credentials might be rolled and if you forget to update the job your primary database could fill up.

Perhaps you could have a second cron job that runs to verify that the first one completed. It could look for a last-ran entry. You should put it in the same database, so maybe perhaps you could a key value store like redis for that.

This is more than a few leaps of logic. a bad config of any infrastructure can cause problems