Micro optimization -- use tuples throughout backend indexing (#9009)

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>
Co-authored-by: Deepak Cherian <deepak@cherian.net>
Co-authored-by: Anderson Banihirwe <13301940+andersy005@users.noreply.github.com>
Co-authored-by: Anderson Banihirwe <axbanihirwe@ualr.edu>

Author: 3 people