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 (
    81610, 81595, 81654, 81637, 81619, 81590, 
    81662, 81649, 81632, 81706, 81615, 
    81639, 81697, 81652, 81622, 81660, 
    81669, 81693, 81628, 81700, 81606, 
    81644, 81703, 81601, 81687, 81679, 
    81666, 81683, 139611, 81689, 81674, 
    151100, 151062
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00101

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "46.27"
    },
    "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": 33,
      "rows_produced_per_join": 33,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "39.67",
        "eval_cost": "6.60",
        "prefix_cost": "46.27",
        "data_read_per_join": "225K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_descriptions`.`product_id` in (81610,81595,81654,81637,81619,81590,81662,81649,81632,81706,81615,81639,81697,81652,81622,81660,81669,81693,81628,81700,81606,81644,81703,81601,81687,81679,81666,81683,139611,81689,81674,151100,151062)) and (`webmarco`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}