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.unit_name 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    23535, 23536, 23537, 23538, 23539, 23540, 
    23541, 23542, 23543, 23544, 23545, 
    23546, 23547, 23548, 23549, 23550
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "product_id", "idx_product_lang"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["product_id", "lang_code"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_product_descriptions.product_id in (23535,23536,23537,23538,23539,23540,23541,23542,23543,23544,23545,23546,23547,23548,23549,23550) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
23535 Protector-wiring<p>Part number 91961T1300</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23536 Protector-wiring<p>Part number 91961T1320</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23537 grommet<p>Part number 91981C1100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23538 Wiring Assembly - Follower<p>Part number 91542AR520</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23539 grommet<p>Part number 915803A500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23540 Junction Block-Sub<p>Part number 91945AR500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23541 Protector-wiring<p>Part number 91961AR130</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23542 Protector-wiring<p>Part number 91961AR140</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23543 Protector-wiring<p>Part number 91961AR150</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23544 Protector-wiring<p>Part number 91961AR160</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23545 Protector-wiring<p>Part number 91961AR220</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23546 Protector-wiring<p>Part number 91961AR230</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23547 Protector-wiring<p>Part number 91961AR370</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23548 Hose Assembly - Rear Washer<p>Part number 98950AR000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23549 grommet<p>Part number 91981J6030</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
23550 Wiring assembly - rear door left<p>Part number 91620AR020</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>