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 (
    83565, 83077, 83574, 90913, 90992, 83057, 
    83058, 83606, 83607, 89825, 89826, 
    89877, 89878, 89949, 89950, 90893, 
    90894, 90972, 90973, 91515, 91516, 
    85060, 85146, 85192, 85238, 86134, 
    86136, 86157, 86159, 86642
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00107

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.80"
    },
    "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": "13.80",
        "eval_cost": "3.00",
        "prefix_cost": "16.80",
        "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 (83565,83077,83574,90913,90992,83057,83058,83606,83607,89825,89826,89877,89878,89949,89950,90893,90894,90972,90973,91515,91516,85060,85146,85192,85238,86134,86136,86157,86159,86642)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}