Sometimes it is necessary to do something after a post was saved. When using the old hooks like save_post and post_updated, the result is not as expected with the block editor: the metadata values are the old ones from before saving.
The rest_after_insert_{$this->post_type} action hook comes to the rescue ({$this->post_type} needs to be replaced with the post type, for example, post or page). It gets the post object as the first param and when fetching data via get_post_meta(), we get the correct data.