/**
 * Implements hook_entity_insert().
 */
function {{ machine_name }}_entity_insert(Drupal\Core\Entity\EntityInterface $entity) {
  // Insert the new entity into a fictional table of all entities.
  \Drupal::database()->insert('example_entity')
    ->fields([
      'type' => $entity->getEntityTypeId(),
      'id' => $entity->id(),
      'created' => REQUEST_TIME,
      'updated' => REQUEST_TIME,
    ])
    ->execute();
}