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 (
    86807, 86846, 89732, 89374, 83117, 83127, 
    83136, 89292, 82352, 89287, 86231, 
    90122, 86819, 86821, 89272, 89275, 
    91292, 89357, 90094, 90104, 90113, 
    91937, 91939, 91940, 91941, 91942, 
    91943, 89201, 89271, 89274
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "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": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "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 (86807,86846,89732,89374,83117,83127,83136,89292,82352,89287,86231,90122,86819,86821,89272,89275,91292,89357,90094,90104,90113,91937,91939,91940,91941,91942,91943,89201,89271,89274)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}