Synch phplistdb with a postgres database

Hi, in order to keep two databases synched about blacklist, list (un)subscriptions, etc, is there a smarter way than investigating any single user?
I’m looking for a table/column where to search into to identify only the users who made changes (for example phplist_user_user_history) instead of scanning the entire list of subscribers. Any suggestion about what and where to look for?

In the (very remote) case anyone was interested in checking the changes made in the last 30 days in order to keep phplistdb synched with another database (and have a sort of report to work with), I preliminarily filtered the search in the database with this query:
SELECT userid, email, DATE_FORMAT(date,’%d/%m/%Y’), summary
FROM phplistdb.phplist_user_user_history
JOIN phplist_user_user ON phplist_user_user_history.userid =
WHERE date > now() - INTERVAL 30 day ORDER BY date DESC;

please, advise if I’m missing something relevant (@duncanc)