SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description, 
  cscart_product_descriptions.meta_keywords, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.promo_text 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    8418, 8415, 8417, 8403, 8409, 8396, 8399, 
    8416, 8404, 8398, 8420, 8394, 8419, 
    8401, 8400, 8402, 8412, 8407, 8393, 
    8411, 8408, 8406, 8405
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00060

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.11"
    },
    "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": 23,
      "rows_produced_per_join": 23,
      "filtered": "100.00",
      "index_condition": "((`primapearl_r_new`.`cscart_product_descriptions`.`product_id` in (8418,8415,8417,8403,8409,8396,8399,8416,8404,8398,8420,8394,8419,8401,8400,8402,8412,8407,8393,8411,8408,8406,8405)) and (`primapearl_r_new`.`cscart_product_descriptions`.`lang_code` = 'ru'))",
      "cost_info": {
        "read_cost": "13.81",
        "eval_cost": "2.30",
        "prefix_cost": "16.11",
        "data_read_per_join": "87K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "meta_keywords",
        "meta_description",
        "search_words",
        "promo_text"
      ]
    }
  }
}