SELECT 
  * 
FROM 
  cscart_product_options_inventory 
WHERE 
  product_id = 516 
  AND combination_hash = '3317745038'

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
516 ATR-DPY-B900-M4A 3317745038 996_19616 4.00 N 0 575.40 30.00 0 0 0 0 118