Report Performance with Data Volume

[PBI_RH]

We have one power bi report published to Power Bi Service. user large dataset storage format. 
the dataset with 1 year data is about 3 GB,
the dataset with 3 years data is about 6.5 GB.
There is one Matrix visualization in the report, I tested the DAX query in DAX studio.
the Query performance is almost the same for 1 year and 3 years data.
seems the data volumne didn't impact the performance which is good, but I want to know why.
Can anybody let me know why this happen? thank you for your help in advance. 

[GilbertQ · Accepted solution]

Hi @PBI_RH 

This is because all the data is stored in memory and long with the compression  of the data it makes it super fast to query analytical workloads. This is a very basic way to explain but that is overall what makes it run so fast.