A query with a large IN () section will be stuck in statistics and use up all RAM. Multiple such queries will crash the server regardless of memory limitations specified in my.cnf
I noticed this in 10.2.35. Downgrading to 10.2.34 fixes the problem
An example is the WordPress "select post_id,meta_value from wp_postmeta where meta_id in (1,2,3 etc ...)" query.