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 (
    262454, 173883, 271489, 271497, 271493, 
    271504, 271500, 271506, 271496, 271492, 
    271498, 224456, 271510, 271503, 271494, 
    271490, 271502, 271505, 271509, 271508, 
    271499, 271507, 271501, 224454, 254325, 
    435505, 381725, 432250
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00105

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "39.26"
    },
    "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": 28,
      "rows_produced_per_join": 28,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "33.66",
        "eval_cost": "5.60",
        "prefix_cost": "39.26",
        "data_read_per_join": "191K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_descriptions`.`product_id` in (262454,173883,271489,271497,271493,271504,271500,271506,271496,271492,271498,224456,271510,271503,271494,271490,271502,271505,271509,271508,271499,271507,271501,224454,254325,435505,381725,432250)) and (`webmarco`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}