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 (
    17, 171996, 121248, 143251, 162699, 
    121501, 177837, 131575, 135087, 155693, 
    137836, 134775, 170928, 172389, 158791, 
    123506, 150952, 160442, 165526, 178218, 
    139924, 125271, 153879, 147591, 170626, 
    164771, 119866, 128957, 146234, 161829, 
    148692, 139499
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00265

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0564324,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["product_id", "lang_code"],
          "loops": 1,
          "rows": 32,
          "cost": 0.0564324,
          "filtered": 100,
          "attached_condition": "cscart_product_descriptions.product_id in (17,171996,121248,143251,162699,121501,177837,131575,135087,155693,137836,134775,170928,172389,158791,123506,150952,160442,165526,178218,139924,125271,153879,147591,170626,164771,119866,128957,146234,161829,148692,139499) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}