Best approach to get data from ECC/s4hana and merge with CAPm

Dear experts,

I have an API that gets a list of data in local ECC and merges this data with some tables in the cloud using CAPm in Java (foundry).

Both data (ECC and cloud) must apply filters from the sapui5 application.

As you can imagine, this approach is underperforming. We decided to create batch operations to get data from 100 to 100.

Could someone explain a better approach?

I think the data replication service exists in SCP, but in this case it is not possible to activate it :(

Thanks in advance

Enric