This plugin is no longer needed. The custom table code is now part of Action Scheduler version 3.0 and newer. If you're using the latest Action Scheduler, you have the most performant schema available.
This can be done either by checking for the existence of a method like action_scheduler_register_2_dot_1_dot_0(), or by using ActionScheduler_Versions::get_versions() (which has existed since AS 1.0.0).
We added a bunch of things to Action Scheduler, mostly around the admin UI, so that it could fully handle custom data stores, like this one.
Because of that, and because we rely on certain methods only available in AS 2.1.0 and newer, like those added in https://github.com/Prospress/action-scheduler/pull/191/commits/bca46a8a34424039621c0fb8acc547280245f48f, this plugin should be updated to require AS 2.1.0 to be active before loading itself.
This can be done either by checking for the existence of a method like
action_scheduler_register_2_dot_1_dot_0(), or by usingActionScheduler_Versions::get_versions()(which has existed since AS 1.0.0).