SELECT 
  * 
FROM 
  cscart_product_options_inventory 
WHERE 
  product_id = 10108 
  AND combination_hash = '1018296218'

Query time 0.00021

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
10108 MDM-RA-BR300-8004 1018296218 178_4240 0.00 N 0 8.96 0.30 1 0 5 0 100