SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    303, 304, 305, 328, 310, 311, 312, 313, 
    314, 315, 316, 317, 318, 319, 320, 321, 
    327, 291, 292, 307
  )

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "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 (303,304,305,328,310,311,312,313,314,315,316,317,318,319,320,321,327,291,292,307)"
        }
      }
    ]
  }
}