I'm learning to use PHP's APC User Cache (APCu) to work with cache on the website.To create a further layer of protection, I would make a cached middle-layer between the web and the game-server, so you don't access the database too frequently (besides crucial functions like login, create stuff, etc.)
Do you mean open port 3306 on the server machine's firewall only to the website machine's IP?Now since you have a middle layer, you don't have just to leave the 3306 port simply open. You can add further security, by opening the 3306 specifically to the middle-layer IP.
I don't know how to do this =(Then, you block the middle layer to be accessible only via the web server. (Maybe Cors)
Let's say I would only use phpmyadmin in very rare cases.Note:
I would open PHPMyAdmin on a different port, and block that port to specific IP addresses. Opening 80 just to access it is not optimal, and opens short periods of vulnerability.
Source: Understanding The Difference Between SQL And MySQL (https://www.simplilearn.com/tutorials/sql-tutorial/difference-between-sql-and-mysql)Actually, MySQL is an RDBS. SQL is the language...