In 3.0 when the banlist table had many rows the pages which displays the banlist was still generated very fast.
However in 3.1 the pages are generated very very slow.
3.0 - 24219 rows
3.1 - 5770 rows
Although the 3.1 board has way less rows it tooks about 10x longer.
Originally mentioned here: https://www.phpbb.de/community/viewtopic.php?f=33&t=231868 (german)