What does my MariaDB do there? And why does it take so long?

Using HAOS and MariaDB for quite a long time. I have some sensors that provide several sensors that update once a second, so produce quite some data. I already removed on device that has 12 entities.
But still some energy consumption is stored very often etc …

My MariaDB file is 2Gb large. No idea if this is ok’ish or huge or whatever …

Purging is set to 7 days, but I don’t know at what time this happens.

I now see heavy load (1 CPU core 100%) for several hours every morning, and would like to know what this is, and if this is expected behaviour?! It also took like 6.5h this morning, which I think is not ok?

Thank you!