rendering performance very slow with zoomlevel > 9

Hi there @all

I tried to setup an experimental tile server hosting only Germany using the following instructions: https://switch2osm.org/serving-tiles/manually-building-a-tile-server-ubuntu-22-04-lts/

Everything works fine in general, but when I try to access a tile with zoomlevel > 9 (10/0/0 e.g.), the rendering time increases from around 0.5s up to > 100s.

My server specs are

1. 6 vCore Processor
2. 12GB RAM, Swapping enabled with 2GB
3. 240GB SSD, currently ~42% in use with data for whole Germany

Compared to the minimum requirements mentioned to host data for the whole world, I thought this could be enough for having only a few users around the day.

Does anyone have an idea for the cause of this huge performance step? Or is it simply far too much load for this server spec?

Currently, I consider pre-rendering tiles up to zoomlevel 15 for Germany using render_tiles_geo.pl script.

Best Sebastian