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 (
    83897, 83898, 83900, 83901, 83902, 83903, 
    83904, 83905, 83906, 91735, 91736, 
    91737, 91738, 91739, 91740, 91741, 
    91742, 91743, 91744, 91745, 91746, 
    91747, 91748, 91749, 91750, 91751, 
    91752, 91753, 91754, 91816
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "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": 30,
      "rows_produced_per_join": 30,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (83897,83898,83900,83901,83902,83903,83904,83905,83906,91735,91736,91737,91738,91739,91740,91741,91742,91743,91744,91745,91746,91747,91748,91749,91750,91751,91752,91753,91754,91816)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}