Original report: https://forum.mattermost.org/t/database-massive-growth-5-12/7576/5
In 5.12, the Jobs subsystem was incorrectly used to schedule plugin key value store cleanups, triggering once a minute and recording a new entry in the Jobs table as a result. We should change the cleanup strategy, and add a migration to remove these records from the Jobs table altogether.
Start job server
Query Jobs table
Expect one new plugin entry per day, not one per minute (should be enough to verify after 5 minutes)