Plasmashell and kwin_x11 consume a lot of CPU if multiple expiring notices are visible at the same time.

STEPS TO REPRODUCE
1. In a konsole bash shell execute many 20-second notifications:

  for i in 1 2 3 4 5 6 7 8 9 10; do notify-send --expire-time 20000 test $i;done

OBSERVED RESULT
Unresponsive/jerky desktop. High CPU usage.  Window dragging is very jerky.  Performance returns to normal as notices expire.

EXPECTED RESULT
No substantial effect on desktop responsiveness or CPU consumption.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: OpenSUSE Tumbleweed 20211005
(available in About System)
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.15.2
Qt Version: 5.15.2

ADDITIONAL INFORMATION
Processors: 6 x AMD-6300
Memory: 15.5 GiB
Graphics Processor: NVIDIA GeForce GTX 1650 SUPER with proprietary driver.