SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12520, 12497, 12528, 12512, 12511, 12527, 
    10580, 10579, 9931, 12521, 12504, 12502, 
    12505, 13099, 12514, 12513, 9759, 10496, 
    10560, 10561
  )

Query time 0.00083

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 20,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (12520,12497,12528,12512,12511,12527,10580,10579,9931,12521,12504,12502,12505,13099,12514,12513,9759,10496,10560,10561)"
    }
  }
}