how to optimize SESSION on codeigniter ?

hello folks

i have mid-range web application that serve at least 40.000 traffic per day ( based on google analytics ) 

i want to know whether you guys that already develop a mid or hi range kind of application also face this kind of problem like mine or not ?

i got an issue with CI session always taking so much resource in our database and sometimes causing a dead lock also 

currently we are using MYSQL database from AWS RDS




as you can see, there always a time when the session spiking and causing slow ( sometimes until deadlock ) in our web apps

and for your information

i also comment this line of code before to prevent session being locked cause if not it will become worse, our application will become super slow




please kindly share me a guidance on how to optimize CI Session using database

thank you