General Issues

Dear Savers , I'm doing lot's of work with FreeRadius , but I'm stuck with 3 major issues. * What is the best max_pps that can handle heavy load , also what is best database software that can handle heavy load . * Doing some modifications to default sites-available what is best way to implement modifications in database queries for custom purpose . * Is modified the queries of the FreeRadius to lower the load like shrink the data being inserted or updated. Will effect the FreerRadius as all Thanks ,