SELECT 
  * 
FROM 
  cscart_product_options_inventory 
WHERE 
  product_id = 525 
  AND combination_hash = '771665148'

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
525 BUD-UW50-05-30 771665148 1360_24266_755_16337_1361_24268 0.00 N 0 9.48 24000.00 0 0 0 0 10