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 (
    414502, 424699, 381632, 431672, 414375, 
    393012, 396068, 393013, 427473, 366897, 
    392222, 414480, 434596, 414400, 391702, 
    387084, 434591, 434595, 435213, 434592, 
    414498, 434594, 434593, 414414, 432460, 
    432542, 432589, 432449, 432642, 432668, 
    432523, 432652, 432688, 432694
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00362

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "47.67"
    },
    "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": 34,
      "rows_produced_per_join": 34,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "40.87",
        "eval_cost": "6.80",
        "prefix_cost": "47.67",
        "data_read_per_join": "232K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_descriptions`.`product_id` in (414502,424699,381632,431672,414375,393012,396068,393013,427473,366897,392222,414480,434596,414400,391702,387084,434591,434595,435213,434592,414498,434594,434593,414414,432460,432542,432589,432449,432642,432668,432523,432652,432688,432694)) and (`webmarco`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}