Why does the Qlik Sense Memory usage remain high?

[Lisa_Sun]

Qlik Sense memory consumption remains at high usage even with a low amount of active users and apps. 

Environment:

Qlik Sense Enterprise on Windows  

The Qlik Engine is an in-memory engine. It will retain applications in memory and only release allocated RAM once the App cache time has been reached. App cache time denotes the number of seconds that a Qlik Sense app is allowed to remain in memory after the last session that used the app has ended. (Source: Engines)

For additional information, see:

QlikView and Qlik Sense resource usage and the Qlik Associative Engine Memory Management and CPU Uti... 
Load Balancing in Qlik Sense 
Qlik Sense® Recommended Product Boundaries