Actually the index can only fail because of a deadlock or a unique failure. Deadlocks are rare and are probably an Application bug and for unique failure you ne

Actually the index can only fail because of a deadlock or a unique failure. Deadlocks are rare and are probably an Application bug and for unique failure you need to fix your database anyway and you either need to drop and recreate it or reinfect it (new stuff will use the index for unique checks even in invalid state but not for queries)