SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.short_description, 
  cscart_product_descriptions.full_description, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.meta_keywords, 
  cscart_product_descriptions.page_title, 
  cscart_product_descriptions.promo_text, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    12, 148, 5, 23, 1, 149, 79, 238, 239, 172, 
    167, 8
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00058

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "28.81"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 12,
      "rows_produced_per_join": 12,
      "filtered": "100.00",
      "index_condition": "((`danishecarter_31jan`.`cscart_product_descriptions`.`product_id` in (12,148,5,23,1,149,79,238,239,172,167,8)) and (`danishecarter_31jan`.`cscart_product_descriptions`.`lang_code` = 'ru'))",
      "cost_info": {
        "read_cost": "26.41",
        "eval_cost": "2.40",
        "prefix_cost": "28.81",
        "data_read_per_join": "54K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "meta_keywords",
        "meta_description",
        "search_words",
        "page_title",
        "promo_text",
        "unit_name"
      ]
    }
  }
}