Optimization, Fixing and Modification of Codeignitor site

We have an existing codeignter portal yet to be launched that needs certain features to be added, modified and fixed. Further, we need the mysql queries in the project to be optimized to ensure efficient fetching of data from our database. The work involves backend as well as frontend skills. The existing project is in Codeigniter 3 and is basically an intercace for vendors for our marketplace linked to our existing running ecommerce website.
We are looking for developers versed in codeignitor who are also comfortable with core PHP and core javascript.