Fix CPU overload caused by PostgreSQL used by Java Spring backend

Our backend runs Java Spring + Hibernate + PostgreSQL DB on an Ubuntu server. We face issues on a server side periodically: CPU usage goes up to 100%, system CPU time rises as well while iowait stays the same. The issue lasts for a couple of days and then returns to the old normal levels. From what we understand it's not long queries execution, it's not the backend itself. Also it's not periodical schedulers or backup routines. It seems like it's smth inside Postgre DB while we do not see anything special in DB logs. We are looking for a specialist who has deep knowledge of how PostgreSQL works (especially in conjunction with Java Spring and Hibernate), has experience of optimization of interaction between the database and the backend software. If you apply for this job, please, include description of relevant experience resolving similar cases in your first message. I do not recommend to generate responses with AI tools as your accounts will be reported.