The user and db tables in the mysql database store information about user privileges. The user table stores global privileges, while the db table stores database-level privileges.

The relay log stores the changes that have been received from the primary server and are awaiting application on the replica server.

The INDEX command in MySQL creates an index on one or more columns, speeding up the retrieval of data during query execution.

MySQL Enterprise Firewall works by analyzing incoming queries in real time and blocking unauthorized or potentially harmful queries, such as those that might be part of a SQL injection attack.

Asynchronous replication is most vulnerable to data loss because the primary server does not wait for the replicas to confirm that they have applied changes. If the primary server crashes, there may be unreplicated transactions.