Have you noticed.
 

One intensive task in any one serverside npc seems to keep every other serverside npc from working?

Specifically DataBase npcs. :-(

Just use smart coding techniques.

Then you're coding very inefficiently -_-
If you are coding things that stall the NPC Server then you need to get rid of them. Sendpm I would venture to say? Sendpm is nice when you sparringly. But then people go and use it to send mass messages and systems and it causes more lag. The less serverside you have to use, the less lag it causes.
---Shifter

avoid timeout loops serverside if at all posible, also nested for-loops and very long for-loops are bad aswell. Although you can do them, just they cant be a very popular NPC (meaning, run over and over again very often, one time use or rarely used forloops are ok)

Yes. :)

Congradulate me, for I have become a lag conscious serverside scripter who realizes the ups and downs of serverside scripts, and is fully capable of delagging npc's of all kinds. :D

"Your training is complete my son. Go out and do good"