Replicate database Supports async only?

I am asking that the ‘replicate database’ command can quickly replicate PB-sized data.
I checked for fast replication of data that is inserted and updated.
However, I would like to load large data in the secondary cluster before the replication command, and then perform the replication command. Please make a suggestion.

Also, you said that clusters are only replicated asynchronously.
Are you planning to have synchronous replication in the future?

The Replicate Database command is usually used across regions, so the overhead from sync replication would be large. We are not planning on having synchronous replication for cross cluster replication.

If the large data load is for a different database, that will be fine, however Replicate will create a new database for the replication. I would recommend starting the Replicate, then doing the load on the master cluster.