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 (
    48805, 36300, 49019, 43649, 44278, 47967, 
    47594, 47865, 33698, 41366, 43853, 
    40928, 44575, 37292, 36293, 48680, 
    48801, 48541, 48804, 48150, 44941, 
    47176, 47607, 47622, 41012, 44752, 
    48791, 44574, 48790, 47177, 35705, 
    47608
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.02775

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 (48805,36300,49019,43649,44278,47967,47594,47865,33698,41366,43853,40928,44575,37292,36293,48680,48801,48541,48804,48150,44941,47176,47607,47622,41012,44752,48791,44574,48790,47177,35705,47608) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}