Hi Benoit,
_changes: per database so not usefull here update notification: my understanding is that it work only on stat level
I believe update notification can handle this, since database creation and deletion send different status messages to the update notification process, so you can use them for now, but they're kind of a pain, and they're going away at some, and when that happens, I'm not sure what the alternative is. I've filed a feature request bug in JIRA for some enhancements to the _changes feeds, so you could have a look there and see whether that would solve your problems:
https://issues.apache.org/jira/browse/COUCHDB-390 -- - eric casteleijn http://www.canonical.com
