The GrowthExperiments extension has a feature called "Recent questions" where we show the user a preview of recent questions that they've asked their mentor or the wiki help desk.
The questions are edits adding new sections to a wiki talk page.
The recent questions feature works by taking an extract of the user's comment and storing it in a JSON blob in the user_properties table, then we can present the user's recent questions on Special:Homepage:
To reduce database usage in the user_properties table we could use a database table to store this information.
Alternatively, we could rethink how this feature functions by using a query to find contributions by the user to the mentor/help desk talk page, and attempt to retrieve the extract on page load time or via a separate API request (so "your recent questions" would not render on server-side) – perhaps there is an easy and/or efficient way to do this via DiscussionTools APIs.