You can configure virtual replicas from the 3.10.0 extension version and above.
To configure Virtual Replica for Sorting, go to Stores > Configuration > Algolia Search > Instant Search Result Page > Use Virtual Replica.
When you switch to Virtual Replica, Algolia deletes the Standard Replica and creates a corresponding Virtual Replica index. Virtual Replica slightly increases the primary index’s size (less than 10 MB per million records), but they don’t affect the number of records. For more information, see What are virtual replicas?.
Starting from version 3.14.0 of the extension, virtual replicas can be configured granularly by attribute or store. Each sorting attribute in Magento generates either a standard or virtual replica index in Algolia, based on whether the Enable Virtual Replica? setting is selected.
Please note that Virtual Replica is only available on Premium plans.