Storage handlers control the loading, saving, and deleting of an entity. The \Drupal\Core\Entity\ContentEntityType provides the base entity type definition for all content entity types. If it is not specified, then the default storage handler is \Drupal\Core\Entity\Sql\SqlContentEntityStorage. This class can be extended to implement alternative load methods or adjustments on saving.
In this recipe, we will implement a method that supports loading an entity by a specific property instead of having to write a specific loadByProperties method call.