So I'm developing a PHP/MySQL based CMS which requires PHP 5.1 and MySQL 5.0 (with InnoDB support) at least. I'm now wondering what features of MySQL I can safely use without noticing one day that "Oh, well, that crappy hoster has disabled feature X, damn, now I'm screwed." So my question is, which of these features can become problematic (= can be disabled, require special configuration, require user privilege): transactions and FKs in InnoDB (of course unavailable to MyISAM) table locking (MyISAM and InnoDB) stored procedures I just want to know once and for all what's the minimal feature set I can expect from MySQL.