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 (
    2001, 36500, 5474, 27854, 41370, 46273, 
    793, 40535, 4293, 5962, 5464, 2453, 
    2158, 48683, 353, 2160, 41416, 4291, 
    2008, 44753, 37307, 1744, 29700, 36295, 
    4872, 48677, 48684, 4464, 5595, 4806, 
    41438, 41356
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.01075

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "11",
          "used_key_parts": ["product_id", "lang_code"],
          "rows": 32,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (2001,36500,5474,27854,41370,46273,793,40535,4293,5962,5464,2453,2158,48683,353,2160,41416,4291,2008,44753,37307,1744,29700,36295,4872,48677,48684,4464,5595,4806,41438,41356) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}