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.meta_keywords, 
  cscart_product_descriptions.meta_description, 
  cscart_product_descriptions.search_words, 
  cscart_product_descriptions.promo_text, 
  cscart_product_descriptions.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    394, 402, 129, 126, 147, 152, 1041, 818, 
    816, 66, 27, 28, 1159, 1160, 1158, 1164, 
    1165, 119, 120, 121, 731, 90, 82, 829, 
    1007, 1006, 1003, 1004, 1005, 108, 109, 
    110, 1318, 92, 80, 55, 140, 134, 350, 
    21, 91, 136, 135, 1228, 933, 1239, 70, 
    123
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00152

JSON explain

{
  "query_block": {
    "select_id": 1,
    "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"],
      "rows": 48,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (394,402,129,126,147,152,1041,818,816,66,27,28,1159,1160,1158,1164,1165,119,120,121,731,90,82,829,1007,1006,1003,1004,1005,108,109,110,1318,92,80,55,140,134,350,21,91,136,135,1228,933,1239,70,123) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description meta_keywords meta_description search_words promo_text unit_name
21
27
28
55
66
70
80
82
90
91
92
108
109
110
119
120
121
123
126
129
134
135
136
140
147
152
350
394
402
731
816
818
829
933
1003
1004
1005
1006
1007
1041
1158
1159
1160
1164
1165
1228
1239
1318