SELECT 
  product_descriptions.product_id, 
  product_descriptions.short_description, 
  IF(
    product_descriptions.short_description = '' 
    OR product_descriptions.short_description IS NULL, 
    product_descriptions.full_description, 
    ''
  ) AS full_description 
FROM 
  product_descriptions 
WHERE 
  product_descriptions.product_id IN (
    186231, 109593, 103373, 193286, 90945, 
    168820, 96320, 90935, 120747, 98810, 
    98813, 98373, 91613, 98734, 104426, 
    91612, 167731, 109606, 98342, 155430, 
    239125, 133812, 196685, 168828, 138080, 
    133813, 133814, 138365, 125527, 221443, 
    138079, 111401
  ) 
  AND product_descriptions.lang_code = 'en'

Query time 0.00427

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "26.93"
    },
    "table": {
      "table_name": "product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "11",
      "rows_examined_per_scan": 32,
      "rows_produced_per_join": 32,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "23.73",
        "eval_cost": "3.20",
        "prefix_cost": "26.93",
        "data_read_per_join": "163K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`goimagine`.`product_descriptions`.`product_id` in (186231,109593,103373,193286,90945,168820,96320,90935,120747,98810,98813,98373,91613,98734,104426,91612,167731,109606,98342,155430,239125,133812,196685,168828,138080,133813,133814,138365,125527,221443,138079,111401)) and (`goimagine`.`product_descriptions`.`lang_code` = 'en'))"
    }
  }
}