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 (
    371, 369, 368, 362, 228, 219, 218, 217, 
    212, 211, 210, 209, 207, 206, 204, 202, 
    197, 196, 195, 192, 189, 187, 184, 181, 
    177, 155, 154, 151, 82, 71, 51, 10, 9
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00054

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "23.11"
    },
    "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": 33,
      "rows_produced_per_join": 33,
      "filtered": "100.00",
      "index_condition": "((`betaatif_store`.`cscart_product_descriptions`.`product_id` in (371,369,368,362,228,219,218,217,212,211,210,209,207,206,204,202,197,196,195,192,189,187,184,181,177,155,154,151,82,71,51,10,9)) and (`betaatif_store`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "19.81",
        "eval_cost": "3.30",
        "prefix_cost": "23.11",
        "data_read_per_join": "125K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ]
    }
  }
}