Everytime you do optimize MySQL, by using mysqlcheck -A -o or using ./mysql_optimize from here.
You may see the output
Table does not support optimize, doing recreate + analyze instead.
It is because the table that you are using is InnoDB.
You can optimize the InnoDB tables by using this.
ALTER TABLE table.name ENGINE='InnoDB';
This will create a copy of the original table, and drop the original table, and replace to the original place.
Although this is safe, but I suggest you do backup and test first before doing this.
For more additional information, you should read in here