SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    256, 253, 254, 425, 251, 252, 426, 599, 
    600, 601, 257, 258, 525, 255, 526, 602
  )

Query time 0.00042

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": 16,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (256,253,254,425,251,252,426,599,600,601,257,258,525,255,526,602)"
    }
  }
}