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 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    90096, 89193, 83118, 84115, 86815, 89973, 
    89975, 94064, 94065, 94066, 97038, 
    98701, 100150, 100654, 100655, 100656, 
    100657, 100658, 100904
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00068

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "8.57"
    },
    "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": 19,
      "rows_produced_per_join": 19,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "6.67",
        "eval_cost": "1.90",
        "prefix_cost": "8.57",
        "data_read_per_join": "72K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (90096,89193,83118,84115,86815,89973,89975,94064,94065,94066,97038,98701,100150,100654,100655,100656,100657,100658,100904)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}