Type Definition pallet_staking::Invulnerables

type Invulnerables<T: Config> = StorageValue<_GeneratedPrefixForStorageInvulnerables<T>, Vec<T::AccountId>, ValueQuery>;

Any validators that may never be slashed or forcibly kicked. It’s a Vec since they’re easy to initialize and the performance hit is minimal (we expect no more than four invulnerables) and restricted to testnets.