SELECT 
  product_id, 
  amount 
FROM 
  cscart_warehouses_destination_products_amount 
WHERE 
  product_id IN (
    21604, 21607, 21606, 21602, 21599, 21617, 
    21616, 21611, 21595, 21597, 21578, 
    21596, 21577, 21561, 21562, 21563, 
    21610, 21615, 21601, 21598, 21591, 
    21592, 21593, 21594
  ) 
  AND destination_id = 115 
  AND storefront_id = 0

Query time 0.00054

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_warehouses_destination_products_amount",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "idx_storefront_id"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "destination_id", "storefront_id"],
      "rows": 24,
      "filtered": 75,
      "index_condition": "cscart_warehouses_destination_products_amount.destination_id = 115 and cscart_warehouses_destination_products_amount.storefront_id = 0 and cscart_warehouses_destination_products_amount.product_id in (21604,21607,21606,21602,21599,21617,21616,21611,21595,21597,21578,21596,21577,21561,21562,21563,21610,21615,21601,21598,21591,21592,21593,21594)"
    }
  }
}