title explains it. I think saving XP is a little laggy and when done on a timer it can happen in the middle of the round when players are fighting. It should be done at round end every few rounds so players won't lag when action is happening.

then your server hardware isn't powerful enough. saving 32 player's xp does not introduce any noticeable lag, they are threaded queries, it creates 32 threads and should not interrupt gameplay

xp is saved on map change and player disconnect, you notice lag you can set the interval which the xp force saves to a large number