Ongoing issue with problematical swap consuming of MariaDB instance

Hello all,

we keep having problems with one of our MariaDB instances consuming more and more swap since October 2023. You can see a cutout of the swap usage in the attached image.
As a result it crashed several times.

We already tried these things:

• increase of swap (server)
• increase of memory (server) + memory settings (MariaDB instance)
• patch to MariaDB version 10.4.28
• migration to new server (old server CentOS 5)
• major upgrade of MariaDB instance from version 10.4.28 to 10.11.7
• reduce of swappiness (server)
• several restarts (server + MariaDB instance)
• major upgrade of customer application (Pimcore 6.2.3 to 11.4.1)
• major upgrade of MariaDB instance from version 10.11.7 to 11.4.4

We are running out of ideas as the performance_schema does not help either and would be very thankful for support.

Kind regards
Sandra Attermeyer