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 (
    86609, 86610, 86678, 86679, 83022, 83023, 
    90858, 90859, 90937, 90938, 89765, 
    86607, 86676, 82863, 82936, 83009, 
    83445, 83450, 83020, 90856, 90935, 
    82717, 83455, 83079, 83080, 83577, 
    83579, 90916, 90918, 90995
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00049

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.21"
    },
    "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": "13.22",
        "eval_cost": "3.00",
        "prefix_cost": "16.22",
        "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 (86609,86610,86678,86679,83022,83023,90858,90859,90937,90938,89765,86607,86676,82863,82936,83009,83445,83450,83020,90856,90935,82717,83455,83079,83080,83577,83579,90916,90918,90995)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}