DELETE `catalog_product_index_eav_temp` FROM `catalog_product_index_eav_temp
This query as well as one to build it runs constantly but if you search all the source code of m2 that table isn’t even brought up and it also doesn’t exist in the database table list. But it’s definitely in show processlist and makes it impossible to edit or add items. It’ll go away for a while and come back.
I traced it back to this core file: magento/module-catalog/Model/Indexer/Product/Eav/Action/Rows.php
It says it runs from mass product actions but we don’t run those often?