arch-8.x-1.x-dev/modules/product/modules/group/arch_product_group.routing.yml

product_matrix.product:
  path: '/api/product-matrix/{group_id}/{product}'
  defaults:
    _controller: '\Drupal\arch_product_group\Controller\ProductMatrixApiController::product'
  requirements:
    _entity_access: 'product.view'
    product: \d+