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 (
    12993, 12994, 12987, 12988, 12840, 12841, 
    12843, 12844, 12848, 12849, 12850, 
    12842, 12851, 12852, 12839, 12845, 
    12846, 12847, 12836, 12837
  ) 
  AND cscart_product_descriptions.lang_code = 'kk'

Query time 0.00048

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": 20,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (12993,12994,12987,12988,12840,12841,12843,12844,12848,12849,12850,12842,12851,12852,12839,12845,12846,12847,12836,12837) and cscart_product_descriptions.lang_code = 'kk'"
    }
  }
}

Result

product_id short_description full_description meta_keywords meta_description search_words promo_text unit_name
12836
12837
12839
12840
12841
12842
12843
12844
12845
12846
12847
12848
12849
12850
12851
12852
12987
12988
12993
12994