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 (
    95966, 95967, 95968, 95969, 95977, 95978, 
    95979, 95980, 95981, 95982, 95983, 
    95984, 95985, 95986, 95987, 95988, 
    95989, 95990, 95991, 95992, 95993, 
    95994, 95995, 95996, 95997, 95998, 
    95999, 96000, 96001, 96002
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00039

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 (95966,95967,95968,95969,95977,95978,95979,95980,95981,95982,95983,95984,95985,95986,95987,95988,95989,95990,95991,95992,95993,95994,95995,95996,95997,95998,95999,96000,96001,96002)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
95966
95967
95968
95969
95977
95978
95979
95980
95981
95982
95983
95984
95985
95986
95987
95988
95989
95990
95991
95992
95993
95994
95995
95996
95997
95998
95999
96000
96001
96002