A while ago, on every IRE game, at 10AM in the morning (real time) there'd be system lag for 1-2 minutes. Then, at Sunday noon every week, mobs would stop and balances (including say balance) would freeze for a few minutes, but aethers would go fine.

That seems to have stopped a while ago though, and I was just curious as to why since someone brought it up. I was always told it was system maintenance, but if so, shouldn't it still be happening? And why was the Sunday one different to the 10AM one?

It's probably either database backup and optimization. Bet the more involved one happens on Sunday. It sounds like they picked the slow times from their perspective. (Sunday could have been the full backup).

My guess is that the major Rapture upgrade--Remember when development sort of halted because of that--or another patch optimized code so you could do a backup with minimal effect on the server performance. I'm sure maintenance is still going on, but it probably has no effect now on the system.

Ahhh, I remember what you mean. That would explain it.