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 (
    21149, 21150, 21151, 21152, 21153, 21154, 
    21155, 21156, 21157, 21158, 21159, 
    21160, 21161, 21162, 21163, 21164
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00035

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 (21149,21150,21151,21152,21153,21154,21155,21156,21157,21158,21159,21160,21161,21162,21163,21164) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21149 Pad-Trunk Lid Garnish<p>Part number 87368T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21150 Strip-back panel molding NO.1<p>Part number 87374T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21151 Strip-back panel molding NO.2<p>Part number 87375T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21152 Clip-Back Panel Molding Mounting<p>Part number 873783M000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21153 Pad-Back Panel Molding<p>Part number 87378T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21154 Pad-Back Panel Molding<p>Part number 87379T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21155 Molding Subassembly - Back Panel<p>Part number 87380T6000UYH</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21156 Bracket-Tailgate Garnish<p>Part number 87326T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21157 Pad-sealing<p>Part number 87325T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21158 Lamp assembly-rear combination inside, left<p>Part number 92403T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21159 Lamp assembly-rear combination inside, right<p>Part number 92404T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21160 Pad-Antinoise N0.1<p>Part number 87321T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21161 Pad-Antinoise N0.2<p>Part number 87322T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21162 Pad-Antinoise N0.4<p>Part number 87324T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21163 Pad-Antinoise N0.5<p>Part number 87383T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21164 Unit Assembly - Rear View Camera<p>Part number 99240T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>