Yes, I updated the docker image yesterday, which is when this started happening.
I did
git pull
./launcher cleanup
./launcher rebuild app
./launcher cleanup
As for posts and topics, it has 17001 topics, with 178297 posts. They were imported from a phpBB install last year.
Anyway, it eventually got up to 16 instances of that query running, so I just killed them off. They haven’t returned in a few hours. I’ll check if it starts using CPU when that scheduled task starts again.