After update to Civicrm 5.8.0 I got a:
MyISAM Database Engine
Your database is configured to use the MyISAM database engine. CiviCRM requires InnoDB. You will need to convert any MyISAM tables in your database to InnoDB. Using MyISAM tables will result in data integrity issues.
Had a look into the db, found out it's just about three tables:
Is it save to do ALTER TABLE tablename ENGINE=InnoDB;
?