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 (
    96850, 96851, 96852, 96853, 96854, 96855, 
    96856, 96857, 96858, 96859, 96860, 
    96861, 96862, 96863, 96864, 96865, 
    98509, 98510, 100187, 100188, 100189, 
    100190, 100191, 100195, 100196, 100197, 
    100298, 100300
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00065

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "12.62"
    },
    "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": "9.82",
        "eval_cost": "2.80",
        "prefix_cost": "12.62",
        "data_read_per_join": "106K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (96850,96851,96852,96853,96854,96855,96856,96857,96858,96859,96860,96861,96862,96863,96864,96865,98509,98510,100187,100188,100189,100190,100191,100195,100196,100197,100298,100300)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}