SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    303, 304, 305, 310, 311, 312, 313, 314, 
    315, 316, 317, 318, 319, 320, 321, 291, 
    292, 307, 296, 297, 293, 294, 308, 302, 
    306, 309, 298, 299, 300, 301, 295
  )

Query time 0.00057

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": 31,
          "filtered": 100,
          "index_condition": "cscart_products.product_id in (303,304,305,310,311,312,313,314,315,316,317,318,319,320,321,291,292,307,296,297,293,294,308,302,306,309,298,299,300,301,295)"
        }
      }
    ]
  }
}