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 (
    99939, 99940, 99941, 99942, 99943, 99944, 
    99945, 99946, 99947, 99948, 99949, 
    99950, 99951, 99952, 99953, 99954, 
    99955, 99956, 99957, 99958, 99959, 
    99960, 99961, 99962, 99963, 99964, 
    99965, 99966, 99967, 99968, 99969, 
    99970, 99971, 99972, 99973, 99974, 
    99975, 99976, 99977, 99978, 99979, 
    99980, 99981, 99982, 99983, 99984, 
    99985, 99986
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00090

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.63"
    },
    "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",
      "cost_info": {
        "read_cost": "16.83",
        "eval_cost": "4.80",
        "prefix_cost": "21.63",
        "data_read_per_join": "183K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (99939,99940,99941,99942,99943,99944,99945,99946,99947,99948,99949,99950,99951,99952,99953,99954,99955,99956,99957,99958,99959,99960,99961,99962,99963,99964,99965,99966,99967,99968,99969,99970,99971,99972,99973,99974,99975,99976,99977,99978,99979,99980,99981,99982,99983,99984,99985,99986)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}