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 (
    8549, 8567, 8577, 8579, 8583, 8586, 8587, 
    8588, 8592, 8597, 8598, 8602, 8603, 
    8605, 8606, 8607
  ) 
  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 (8549,8567,8577,8579,8583,8586,8587,8588,8592,8597,8598,8602,8603,8605,8606,8607) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
8549 Clip-Trim Mounting<p>Part number 858593S500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8567 Tape-Blanking Hole<p>Part number 81777A9000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8577 Ultrasonic Sensor Assembly-Parking Assist System<p>Part number 99310G9000NCM</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8579 Outside handle & lock assembly-trunk lid<p>Part number 81820T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8583 Molding-rear window<p>Part number 87120G9500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8586 screw-tapping<p>Part number 1243103107B</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8587 screw-tapping<p>Part number 1249305143</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8588 Nut-Flange<p>Part number 1339506007B</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8592 Bolt-Insert<p>Part number 87254D3100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8597 Emblem-G70<p>Part number 86310G9520</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8598 Emblem-AWD<p>Part number 86316G9520</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8602 Lamp assembly-rear combination inside, left<p>Part number 92403G9500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8603 Lamp assembly-rear combination inside, right<p>Part number 92404G9500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8605 Mirror assembly - outside rear view, left<p>Part number 87610G9AJ0NCM</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8606 Mirror assembly - outside rear view, right<p>Part number 87620G9AJ0NCM</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
8607 Actuator assembly - outside mirror, left<p>Part number 87612F6500</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>