SELECT 
  * 
FROM 
  cscart_product_options_inventory 
WHERE 
  product_id = 10183 
  AND combination_hash = '684628764'

Query time 0.00027

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
10183 870P07 80AU06 684628764 1072_20416_1074_20439 0.00 N 0 2995.00 76.00 0 0 0 0 101