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 (
    21293, 21294, 21295, 21296, 21297, 21298, 
    21299, 21300, 21301, 21302, 21303, 
    21304, 21305, 21306, 21307, 21308
  ) 
  AND cscart_product_descriptions.lang_code = 'ru'

Query time 0.00036

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 (21293,21294,21295,21296,21297,21298,21299,21300,21301,21302,21303,21304,21305,21306,21307,21308) and cscart_product_descriptions.lang_code = 'ru'"
    }
  }
}

Result

product_id short_description full_description unit_name
21293 Sensor Assembly - Rear Height, Left<p>Part number 55830T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21294 cap assembly<p>Part number 9216339000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21295 Lamp assembly-head, left<p>Part number 92101T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21296 Lamp assembly-head, right<p>Part number 92102T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21297 Subassembly - headlamp, left<p>Part number 92103T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21298 Subassembly - headlamp, right<p>Part number 92104T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21299 Bracket-headlamp, right<p>Part number 92152T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21300 Tube-Rubber<p>Part number 9216325000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21301 ECU assembly-headlamp<p>Part number 92170T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21302 Bracket-headlamp, left<p>Part number 92151T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21303 Integrated LED control unit - headlamp, left<p>Part number 92183T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21304 Integrated LED control unit - headlamp, right<p>Part number 92184T6100</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21305 LED module - headlamp turn signal, left<p>Part number 92187T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21306 LED module - headlamp turn signal, right<p>Part number 92188T6000</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21307 Garnish-side repeater upper, left<p>Part number 923A7T6010</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>
21308 Garnish-side repeater upper, left<p>Part number 923A7T6000UYH</p><p>If you are not sure about compatibility, please contact us in advance to confirm the part number.</p>