The file:
kernel/classes/datatypes/ezidentifier/ezidentifiertype.php

is locking DB tables. It is a performance issue to lock the DB table "ezcontentobject_attribute".
You would be able to improve the performance when avoiding to lock that table.

The table lock happens in the function "assignValue" and gets executed when creating a new ezp content object that contains an ezidentifier attribute.

Steps to reproduce

create a content class that contains the attribute type "ezidentifier'. Create an instance of that new content class.