MySQL foreign keys add locks to referenced rows, and can have surprising effects on concurrent queries, particularly if you aren't running at read committed or

MySQL foreign keys add locks to referenced rows, and can have surprising effects on concurrent queries, particularly if you aren't running at read committed or lower isolation level. There's also this: https://bugs.mysql.com/bug.php?id=48652 https://bugs.mysql.com/bug.php?id=48652 - still open after all these years (and yes I know there are much longer open bugs).