In production, you likely do not want the package to scan all of your classes on every request. Therefore, during your deployment process, you should run the event-sourcing:cache-event-handlers Artisan command to cache a manifest of all of your application's projectors and reactors. This manifest will be used by the package to speed up the registration process. The event-sourcing:clear-event-handlers command may be used to remove the manifest.
If you want to turn off auto-discovery to enforce manually registration of projectors and reactors, just set the auto_discover_projectors_and_reactors key in the event-sourcing config file to an empty array.