Validating only new karaoke on creation
Looking at the validation rules for karaokes that were implemented by @TheMio, it seems that it is not necessary to validate the whole base upon adding a karaoke because the validity of other karaokes should not be changed by adding a karaoke.
Therefore, we could save a lot of time by validating only the new karaoke.
Not that we can't say the same for editing a karaoke, because you can influence the validity of its children. If I am not mistaken, the smallest subset of karaokes we could validate upon editing to know if all karaokes are valid would be the edited karaoke and all its descendants. The complete list of descendants is more intensive to figure out.