SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12750, 20782, 20306, 23339, 6863, 22527, 
    9296, 20147, 21081, 19788, 20776, 20781, 
    20303, 20304, 20305, 18797
  )

Query time 0.00106

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": 16,
          "filtered": 100,
          "index_condition": "cscart_products.product_id in (12750,20782,20306,23339,6863,22527,9296,20147,21081,19788,20776,20781,20303,20304,20305,18797)"
        }
      }
    ]
  }
}