share data between server applications

You could do it in different ways.

1. You could create some API endpoints so the apps could communicate with each other;
2. You could whitelist each servers IP address and use multiple database connections to grab (and maybe cache, if possible) data to be used as needed;

Personally, independently of the type of information stored on each server, I'd go with option 1 and standardize the communications via an API.

Best regards,
José Postiga
Senior Backend Developer