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 (
    95, 96, 97, 100, 101, 102, 103, 104, 105, 
    106, 107, 108, 109, 110, 111, 112, 113, 
    114, 115, 116, 117, 118, 119, 120
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00056

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "57.61"
    },
    "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": 24,
      "rows_produced_per_join": 24,
      "filtered": "100.00",
      "index_condition": "((`danishecarter_latest`.`cscart_product_descriptions`.`product_id` in (95,96,97,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120)) and (`danishecarter_latest`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "52.81",
        "eval_cost": "4.80",
        "prefix_cost": "57.61",
        "data_read_per_join": "109K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description",
        "unit_name"
      ]
    }
  }
}