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 (
    94809, 94810, 94823, 94824, 94825, 94826, 
    94827, 94828, 94829, 94830, 94831, 
    94832, 94842, 95312, 95313, 95555, 
    95556, 95736, 95737, 95738, 95739, 
    95740, 95741, 95742, 95743, 95744, 
    95745, 95746, 95747, 95748
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00078

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 (94809,94810,94823,94824,94825,94826,94827,94828,94829,94830,94831,94832,94842,95312,95313,95555,95556,95736,95737,95738,95739,95740,95741,95742,95743,95744,95745,95746,95747,95748)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
94809
94810
94823
94824
94825
94826
94827
94828
94829
94830
94831
94832
94842
95312
95313
95555
95556
95736
95737
95738
95739
95740
95741
95742
95743
95744
95745
95746
95747
95748