SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    1399, 1394, 1400, 1398, 1401, 1402, 1403, 
    1404, 1393, 1389, 1384, 1206
  )

Query time 0.00086

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": 12,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (1399,1394,1400,1398,1401,1402,1403,1404,1393,1389,1384,1206)"
    }
  }
}