bear in mind that the best way to configure ProxySQL is through its admin interface.
llow you to control the list of the backend servers, how traffic is routed to them, and other important settings (such as caching, access control, etc)
Once you've made modifications to the in-memory data structure, you must load the new configuration to the runtime, or persist the new settings to disk
mysql_variables: contains global variables that control the functionality for handling the incoming MySQL traffic.
mysql_users: contains rows for the mysql_users table from the admin interface. Basically, these define the users which can connect to the proxy, and the users with which the proxy can connect to the backend servers.
mysql_servers: contains rows for the mysql_servers table from the admin interface. Basically, these define the backend servers towards which the incoming MySQL traffic is routed.
mysql_query_rules: contains rows for the mysql_query_rules table from the admin interface. Basically, these define the rules used to classify and route the incoming MySQL traffic, according to various criteria (patterns matched, user used to run the query, etc.).