SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    21383, 20994, 21025, 21387, 20995, 21026, 
    21388, 20791, 21028, 21393, 22540, 
    20478, 21401, 22541, 20481, 22542, 
    20206, 22543, 20207, 22544, 20210, 
    20999, 20590, 21023, 20337, 21024
  )

Query time 0.00090

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": 26,
          "filtered": 100,
          "index_condition": "cscart_products.product_id in (21383,20994,21025,21387,20995,21026,21388,20791,21028,21393,22540,20478,21401,22541,20481,22542,20206,22543,20207,22544,20210,20999,20590,21023,20337,21024)"
        }
      }
    ]
  }
}