SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    844, 756, 755, 434, 863, 220, 823, 610, 
    867, 858, 635, 1044
  )

Query time 0.00089

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": 12,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (844,756,755,434,863,220,823,610,867,858,635,1044)"
    }
  }
}