How Azure Redis Cache is used in Power BI Service Context

Hi, 

Just going thourgh this article about Power BI Architecture document. 

Can someone please explian how Azure Redis Cache in used in Power BI Service? 

I understand redis cache mostly used in Application context to bring the data into memory, i wonder how is it used in Power BI app context. 

https://docs.microsoft.com/en-us/power-bi/service-admin-power-bi-security

Thanks in Advance