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, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    165, 166, 86, 106, 105, 247, 101, 33, 32, 
    163, 244, 212, 155, 102, 55, 176, 69, 
    138, 110, 36, 206, 28, 184, 183, 133, 
    132, 125, 120, 223, 225, 224, 146, 147, 
    93, 117, 219, 222, 220, 221, 87, 113, 
    139, 118, 83, 157, 123, 174, 171
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00077

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "115.21"
    },
    "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": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "index_condition": "((`danishecarter_25_march`.`cscart_product_descriptions`.`product_id` in (165,166,86,106,105,247,101,33,32,163,244,212,155,102,55,176,69,138,110,36,206,28,184,183,133,132,125,120,223,225,224,146,147,93,117,219,222,220,221,87,113,139,118,83,157,123,174,171)) and (`danishecarter_25_march`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "105.61",
        "eval_cost": "9.60",
        "prefix_cost": "115.21",
        "data_read_per_join": "219K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}