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, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    51497, 51498, 51496, 105, 126, 115, 11, 
    81, 56, 135, 82, 116, 117, 106, 17, 57, 
    122, 58, 5, 22, 18, 27, 119, 121, 23, 141, 
    4, 142, 120, 62, 108, 107
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00104

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "22.41"
    },
    "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": 32,
      "rows_produced_per_join": 32,
      "filtered": "100.00",
      "index_condition": "((`test_uchur_k`.`cscart_product_descriptions`.`product_id` in (51497,51498,51496,105,126,115,11,81,56,135,82,116,117,106,17,57,122,58,5,22,18,27,119,121,23,141,4,142,120,62,108,107)) and (`test_uchur_k`.`cscart_product_descriptions`.`lang_code` = 'ru'))",
      "cost_info": {
        "read_cost": "19.21",
        "eval_cost": "3.20",
        "prefix_cost": "22.41",
        "data_read_per_join": "146K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "meta_keywords",
        "meta_description",
        "search_words",
        "promo_text",
        "unit_name"
      ]
    }
  }
}