I noticed in the app that these queries were slowwww! I was able to
track it down to a bad query plan, as we explain in the comment.
I searched online for "mysql query performance filter on one join table
sort by another", and was surprised to find this answer suggest a
subquery, which I've often been told to expect to be slower compared to
joins? But it certainly worked in this case!
https://stackoverflow.com/questions/35679693/mysql-optimize-join-with-filter-and-order-on-different-tables