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 (
    4812, 1852, 1472, 2464, 1996, 41360, 
    27287, 2251, 41357, 5645, 41363, 45282, 
    45024, 41388, 4290, 3642, 4300, 40929, 
    1995, 41138, 4001, 47610, 40753, 43651, 
    35691, 41410, 31741, 41427, 41359, 
    2640, 1991, 3978
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.02238

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 (4812,1852,1472,2464,1996,41360,27287,2251,41357,5645,41363,45282,45024,41388,4290,3642,4300,40929,1995,41138,4001,47610,40753,43651,35691,41410,31741,41427,41359,2640,1991,3978) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}