Related AWS Premium Knowledge Center Document: - [How do I create another master user for my Amazon RDS DB instance that is running MySQL?](https://aws.amazon.com/premiumsupport/knowledge-center/duplicate-master-user-mysql/)

create_user.sql

CREATE USER 'master_user'@'%' IDENTIFIED BY 'password';
GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, RELOAD, PROCESS, REFERENCES, INDEX, ALTER, SHOW DATABASES, CREATE TEMPORARY TABLES, LOCK TABLES, EXECUTE, REPLICATION SLAVE, REPLICATION CLIENT, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE, CREATE USER, EVENT, TRIGGER ON *.* TO 'master_user'@'%' WITH GRANT OPTION;