(Note, this is a proposed solution for notifications/watchlists with the higher notification level described in T100528: Improve organization and control for Flow notifications (tracking + ideas)). It is not needed with current notification behavior.
[Please edit/improve. Rough non-technical notes. Non-exact keywords within!]
There's the performance/scaling problem of: hundreds of people being auto-subscribed to many highly active pages, each with many new topics, and the watchlist database getting too big too fast.
I.e. one of the LQT scaling problems, from having each post as a separate page.
E.g. if 2,823 people watchlist WP:VPT (they do), which gets very roughly 1,500 new sections a year (based on 30 this week), that's 4,234,500 new watchlisted topics in the database, annually, for one page alone.
Someone suggested this possible solution:
- if an editor is watchlisting a board, with the highest "notification volume" setting (forthcoming in T100528: Improve organization and control for Flow notifications (tracking + ideas)),
- and is therefor essentially "fully auto-subscribed" to every new Flow Topic, but they haven't actually participated, or manually clicked the watchlist-star...
- then it could be a solution to drop these auto-subscriptions from their watchlist table after 1 year (for performance reasons),
- because if they're still watchlisting the page at highest volume, then if the old Topic ever gets active again, it will reappear in their notifications as expected.