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 (
    878, 877, 879, 876, 870, 891, 869, 890, 
    871, 892, 277, 785, 784, 1081, 1079, 
    1080, 1078, 1082, 1083, 1077, 248, 919, 
    269, 821, 822, 278, 279, 302, 303, 720, 
    986, 921, 922, 920, 923, 960, 674, 679, 
    948, 678, 526, 677, 680, 527, 959, 676, 
    675, 896
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00151

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 (878,877,879,876,870,891,869,890,871,892,277,785,784,1081,1079,1080,1078,1082,1083,1077,248,919,269,821,822,278,279,302,303,720,986,921,922,920,923,960,674,679,948,678,526,677,680,527,959,676,675,896) and cscart_product_descriptions.lang_code = 'en'"
    }
  }
}

Result

product_id short_description full_description meta_keywords meta_description search_words promo_text unit_name
248
269
277
278
279
302
303
526
527
674
675
676
677
678
679
680
720
784
785
821
822
869
870
871
876
877
878
879
890
891
892
896
919
920
921
922
923
948
959
960
986
1077
1078
1079
1080
1081
1082
1083