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 (
    90592, 90593, 90588, 90590, 90589, 90591, 
    89249, 89250, 89251, 89252, 90032, 
    90033, 90034, 90035, 90036, 90037, 
    90027, 90028, 90029, 90030, 90031, 
    95360, 96195, 96196, 96197, 96198, 
    96199, 96200, 96201, 100477, 100478, 
    100858, 100859, 100860, 100861, 100862
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00093

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.22"
    },
    "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": 36,
      "rows_produced_per_join": 36,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "12.62",
        "eval_cost": "3.60",
        "prefix_cost": "16.22",
        "data_read_per_join": "137K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (90592,90593,90588,90590,90589,90591,89249,89250,89251,89252,90032,90033,90034,90035,90036,90037,90027,90028,90029,90030,90031,95360,96195,96196,96197,96198,96199,96200,96201,100477,100478,100858,100859,100860,100861,100862)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}