SELECT 
  * 
FROM 
  cscart_product_options_inventory 
WHERE 
  product_id = 636 
  AND combination_hash = '4042646150'

Query time 0.00023

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_product_options_inventory const PRIMARY,pc PRIMARY 4 const 1

Result

product_id product_code combination_hash combination amount temp position price weight min_qty max_qty qty_step list_qty_count aval_status
636 MDM-KD-LCO-8004 4042646150 1218_22769 0.00 N 0 8.68 2.00 0 0 0 0 100