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 (
    400316, 401024, 401027, 401040, 401070, 
    401577, 401589, 401603, 401614, 401618, 
    401630, 402338, 402355, 402360, 402362, 
    402897, 402908, 402938, 403717, 404218, 
    404252, 404994, 405004, 405006
  ) 
  AND product_descriptions.lang_code = 'en'

Query time 0.00190

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "20.38"
    },
    "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": 24,
      "rows_produced_per_join": 24,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "17.98",
        "eval_cost": "2.40",
        "prefix_cost": "20.38",
        "data_read_per_join": "122K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`goimagine`.`product_descriptions`.`product_id` in (400316,401024,401027,401040,401070,401577,401589,401603,401614,401618,401630,402338,402355,402360,402362,402897,402908,402938,403717,404218,404252,404994,405004,405006)) and (`goimagine`.`product_descriptions`.`lang_code` = 'en'))"
    }
  }
}