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 (
    3623, 5761, 40144, 3624, 5763, 4268, 
    4267, 26372, 3629, 49186, 5758, 4307, 
    565, 48845, 5775, 47274, 40802, 3627, 
    1752, 19207, 40893, 4302, 36271, 41616, 
    42371, 5764, 4941, 1442, 5771, 41410, 
    5760, 5773
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.07021

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 (3623,5761,40144,3624,5763,4268,4267,26372,3629,49186,5758,4307,565,48845,5775,47274,40802,3627,1752,19207,40893,4302,36271,41616,42371,5764,4941,1442,5771,41410,5760,5773) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}