Not sure wich team should deal with this but Im reporting this bug to both Acy and Event booking developers.
We have found a problem found in the events booking plugin (Event Booking (tag + filter plugin) v2.2.5 updated on 21 Sep 2017) from Acymailing. It sends an erroneous query to the server causing the blockage of tables and a consumption of 100% cpu per mysql.
Our guess is that the new search system or some of the table changes are interfering with this acymailing plugin.