Hi @Pedro Pinela ,

for starters, I would like to point out, that you don't have to set the second one to Only On Demand, and then call it in the OnAfterFetch of the first to make sure it happens afterwards.  I'm assuming the reason you do this is that the second aggregate has result from the first as input (maybe filter or something)  

If you are sure you will always want to run second, then just put them both on AtStart, and Outsystems will detect and take care of this direct dependency between both of them.

If you are very often not running the second (dependent on details coming back from the first), use your approach with the onAfterFetch, where you can build a condition client side around refresh of the second.

I think 2 consecutive round trips to the server might be slightly slower than 1 big trip in a DataAction retrieving both, but that difference would typically much less important for performance than the queries themselves and the amount of data coming back from them.

An advantage of doing 2 screen aggregates instead of stuffing them in the same DataAction, is that the data coming back from the first aggregate will be visible to the user faster.

Dorine

Hello @Pedro Pinela,

It depends on factors such as data volume, user experience, and control:

Two Aggregates with "Only on Demand":

Pros: Reactive nature, simplicity.

Cons: Extra fetch requests, potential delay.

Data Action:

Pros: Control, caching, flexibility.

Cons: Complexity, need to manage initial load.

Based on your requirement you can consider following things and use accordingly:

Data volume: Large data may impact performance, requiring caching and query optimization.
User experience: Decide between slight delay (aggregates) or more control (data actions).
Caching: Implement caching for performance improvement.
Testing: Perform real-world performance tests to identify the best approach.

The choice depends on specific requirements and trade-offs, and combining both approaches can be beneficial in achieving the desired performance.

Hope it helps!
Thanks