I checked the currently running queries with “mysqladmin processlist“, and almost all (hundreds of them) queued queries are those involving those tables, looking for specific content in the field “ip”. They’re all looked like these: SELECT location FROM wp_statistics_visitor WHERE ip = '...
+myadmin +dance +wwyx +demo1 +wwv +today +explore +price +www21 +fusion +ld +www17 +testapi +trade +wwwa +wwwd +wwxu +caiwu +aaron +maths +wwux +apt +aurora +luna +ww6 +www26 +error +console +static2 +best +hj +australia +www22 +ocean +paris +xd +mx4 +gw1 +...