SELECT 
  cscart_bm_layouts.* 
FROM 
  cscart_bm_layouts 
WHERE 
  1 
  AND is_default = 1 
  AND theme_name = 'toolbox' 
  AND storefront_id = 1

Query time 0.00010

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_bm_layouts ALL is_default 6 Using where

Result

layout_id name is_default width theme_name style_id layout_width min_width max_width storefront_id
2 Main 1 12 toolbox Black fluid 320 1400 1