While investigating the various Gerrit issue we have, notably with memory usage and garbage collection, I eventually found @Owl bot.
Every 30 seconds it does a query such as:
gerrit query limit:100 (status:open OR status:closed)
AND NOT (502978 OR 478688 OR 266726 OR 266725 OR 256050 OR 235852 OR 143269 OR 102114 OR 101842 OR 99101
OR 58858 OR 32902 OR 13930 OR 225009 OR 225033 OR 225080 OR 225087 OR 225099) --all-approvals --comments --format JSON --start 145500
On September 30th some change have been made and the limit is now set to 10. That would in turn mean the bot is crawling for wayy longer.
I have disabled the owl account entirely for now to check whether it improve Gerrit memory / gc pressure. Will reenable it eventually.
I would guess the limit should instead be raised. Probably to 200 or even more if that works.