Hi Dipali,

it's always depend upon the sequence. in which sequence you write. 

Hi @Dipali Shrawane
Data Actions and client-side Aggregates concurrently start to fetch data after the Screen loads. 

Regards
Krishnanand Pathak

HelloSo for the first question - which one is running first ?

When the fetch property of both the Aggregate and Data action is set to  At Start, We cannot say which one will run first and which will run second, It is an asynchronous process, so we can't say which one is going to be executed at first. It will run in random order. Either your data action will run first or your aggregate it is not fixed.

Your Second question -  Yes we can see both are taking the same time. Data action is used when we need to fetch data from Server Action, Rest/Soap API and from SQL Query . Aggregates are used to fetch data from database entities.
So as we know Aggregate return optimize query, so what does optimized means?
It means only attributes which is being used on the screen will be fetched.
But on the other hand, if you will use data action, you have to fetch all the attributes unless you manually decide which one to use via  Advance SQL Querry.
So give it a try with both.
Use Aggregate And Bind some attributes to screen , and use Data action and fetch all data
Then Compare them both.

Thanks
Tousif Khan