This question doesn't have any codes, it's more of a theoretical question. I need guidance on what method to look for. I've searched on google before but found nothing on this specific case.

I have 2 servers(CentOS) where I have MySQL database set up. In one server(server 1) I have Wordpress installation(LAMP) with the database set up. The site is working. However, I want to split the database that is currently on server 1 and host it partially on server 2. Now, I know how to use a remote database in WordPress' wp-config.php file but here I want to use two databases.

In this case, I can try a manual query from the second server. However the reason I want to split the databases because of a single table that includes more than a million entries. Because the table is also going to be split, and the table is wordpress' default post meta table, and I wouldn't know which posts are going to be in which database(more than million entries!), I can't use a custom query. Also I know that default $wbdp only pulls data from 1 database.

To summarize this question, is there any way to use multiple Wordpress Database without having a custom database query?