SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.product, 
  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 (
    104, 2593, 2711, 2710, 2693, 2709, 2976, 
    2735, 2694, 3187, 2990, 4735, 2991, 
    2989, 863, 1478, 1479, 781, 862, 3175, 
    7926, 1480, 1482, 2446, 1481, 6430, 
    6431, 7254, 7255, 4050, 4051, 4602, 
    4049, 4034, 4048, 4419, 4601, 4422, 
    4418, 4421, 4420, 4423, 4600, 5961, 
    5960, 5958, 5959, 5213
  ) 
  AND cscart_product_descriptions.lang_code = 'de'

Query time 0.00064

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "33.61"
    },
    "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": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "index_condition": "((`dbggbern`.`cscart_product_descriptions`.`product_id` in (104,2593,2711,2710,2693,2709,2976,2735,2694,3187,2990,4735,2991,2989,863,1478,1479,781,862,3175,7926,1480,1482,2446,1481,6430,6431,7254,7255,4050,4051,4602,4049,4034,4048,4419,4601,4422,4418,4421,4420,4423,4600,5961,5960,5958,5959,5213)) and (`dbggbern`.`cscart_product_descriptions`.`lang_code` = 'de'))",
      "cost_info": {
        "read_cost": "28.81",
        "eval_cost": "4.80",
        "prefix_cost": "33.61",
        "data_read_per_join": "183K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "product",
        "short_description",
        "full_description"
      ]
    }
  }
}