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 (
    86778, 82633, 82634, 83530, 83531, 85316, 
    85413, 85464, 85515, 86470, 86746, 
    86973, 87034, 89074, 89820, 89872, 
    89944, 91510, 82851, 82862, 82924, 
    82935, 82997, 83008, 83444, 83449, 
    83513, 83521, 85123, 84329
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00085

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.21"
    },
    "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": "13.22",
        "eval_cost": "3.00",
        "prefix_cost": "16.22",
        "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 (86778,82633,82634,83530,83531,85316,85413,85464,85515,86470,86746,86973,87034,89074,89820,89872,89944,91510,82851,82862,82924,82935,82997,83008,83444,83449,83513,83521,85123,84329)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}