SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    10039, 10040, 10756, 10757, 10758, 10397, 
    10398, 10399, 10400, 10401, 10402, 
    12700, 12546, 12633, 12573, 12548, 
    12580, 12576, 12565, 12567
  )

Query time 0.00077

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 (10039,10040,10756,10757,10758,10397,10398,10399,10400,10401,10402,12700,12546,12633,12573,12548,12580,12576,12565,12567)"
    }
  }
}