Does segment cache use lru algo or sth else

Aiming to decrease the num of query,I turned off the refreshment automatically in imply BI. Cuz I found that sometimes even max time query sent by BI encountered timeout problem.
I have no idea how to improve the query performance now since giving more resources didn’t make any change.

I found that our imply bi user send a lot of request, sometimes 200 request per minute for one user. Is there any way to restrict the num of requests? I turned off the automatic refreshing but still so many requests. Do you think is a good idea to increase the num of processing thread?