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 (
    95635, 95636, 95637, 95639, 95641, 95642, 
    95643, 95644, 95647, 95648, 95649, 
    95650, 95651, 95652, 95654, 95683, 
    95702, 95703, 95764, 95766, 95767, 
    95780, 95781, 95782, 95783, 95784, 
    95785, 95829, 95830, 95831
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00084

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 (95635,95636,95637,95639,95641,95642,95643,95644,95647,95648,95649,95650,95651,95652,95654,95683,95702,95703,95764,95766,95767,95780,95781,95782,95783,95784,95785,95829,95830,95831)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id short_description full_description
95635
95636
95637
95639
95641
95642
95643
95644
95647
95648
95649
95650
95651
95652
95654
95683
95702
95703
95764
95766
95767
95780
95781
95782
95783
95784
95785
95829
95830
95831