SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    4, 1, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 
    17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 
    27, 28, 29, 30, 31, 32, 33, 34, 35
  )

Query time 0.00066

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": 32,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (4,1,5,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35)"
    }
  }
}