After a long time having problems with performance going down in our Zope/Storm applications I could now figure out where it is coming from. In my latest app using tornado and Storm I have the same problem. When using List or Pickle properties (both are derived from MutableValueVariable) I found that any time a property is read a flush event hook is added but never removed. The longer the app runs the more hooks are registered which result in low perfomance in store.flush. The flush event hook is unhooked on the 'stop-tracking-changes' event which is only emited if an object is removed from the database. -- Jürgen Kartnaller, senior developer Lovely Systems AG Telefon +43 5572 908060, Fax +43 5572 908060-77 Schmelzhütterstraße 26a, 6850 Dornbirn, Austria