Partial index on Paranoia when using MySQL

how MySQL handles indexes, particularly with respect to conditional indexing or optimizing queries that involve conditions like deleted_at IS NULL? this is based on the readme docs that mentions using this kind of index: https://github.com/rubysherpas/paranoia?tab=readme-ov-file#about-indexes
`add_index :clients, :group_id, where: "deleted_at IS NULL"`