Why doesn't load on MySQL drop after query execution?

Question

PHP

Good day, there is a problem, I can not understand the reason yet. There is a console application in php, which spins in an endless loop and makes requests to the database, respectively, one connection is kept. It is very clearly visible from the graphs in zabbix that when a heavy request starts to be executed, the CPU load level rises and does not fall, after the end of the request, with each such request the load increases. One has only to restart the process, respectively - to break the connection to the base, the load immediately drops.
I would be grateful if someone tells me what the problem could be and in which direction to dig.