• Query optimization: The most most important fact for DB optimization is to tune in your queries for faster data manipulation activities. Frequently check slow query log and tune the heavy resource intensive queries.
• Master-Master Replication:
• In Memory Usage:
• Thread Concurrency:
• RAID: Move your servers disk on RAID environment
• Key Parameters:  Tune our key parameters for faster CRUD operations.

Hope implementing above mentioned techniques you will be able to optimize your MySQL.

Syntax of creating a custom function:

CREATE [OR REPLACE] FUNCTION function_name
[ (parameter [,parameter]) ]
RETURN return_datatype
IS | AS
[declaration_section]
BEGIN
executable_section
[EXCEPTION
exception_section]
END [function_name];

Custom functions may have zero or more parameters in place. There are three types of parameters that can be defined in a custom function.

1. IN: This parameter can be called from a procedure or a function. The value of this parameter cannot be overwritten by procedure or function.
2. OUT: This parameter cannot be called from a procedure or function, but its value can be overwritten from them.
3. IN OUT: It has both the properties of above type. As it can be called from procedure and functions and also can be overwritten by them.

Some examples of creating and calling custom functions:

• Function without parameters.

Function with parameter.